Help with yellowing leaves

Hi there,
I noticed some yellowing leaves yesterday and I don’t exactly know what to do to remedy it. My first thought was maybe the soil isn’t the right pH so I did a slurry test and it came out at 6.8. Reason I thought it was the soil is because when I water this plant I put in water at pH of 7.2 and the run-off is 6.5-6.6. That made me think the soil was real low. But that doesn’t seem to be it. Any ideas from the experienced growers here? @MattyBear, @Covertgrower, @blackthumbbetty, @dbrn32, @PurpNGold74, @garrigan62, @Myfriendis410

Thanks for any input!

Here is an image:

Adding any nutrients to your feeds?
I saved this image and it has helped me alot. I’ll share it for anyone who wants to save it


Kinda looks over watered to me. PH 6.8 at the soil is a bit high. Not sure if that would even be a problem. Might be root bound too.

What soil, nutrient line, cal mag if any etc?

COPY/PASTE the below list into your forum post.

Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so; Or post
NA (non applicable)

  • What strain, Seed bank, or bag seed
  • Method: Soil w/salt, Organic soil, Hydroponics, Aquaponics, KNF
  • Vessels: Pots, Grow beds, Buckets, Troths
  • PH of Water, Solution, runoff (if Applicable)
  • PPM/TDS or EC of nutrient solution if applicable
  • Indoor or Outdoor
  • Light system
  • Temps; Day, Night
  • Humidity; Day, Night
  • Ventilation system; Yes, No, Size
  • AC, Humidifier, De-humidifier,
  • Co2; Yes, No

Always try to upload a clear picture of any issues you may have to allow the community to assist you.

Add anything else you feel would help us give you a most informed answer should be included. Feel free to elaborate, but short and to the point questions and facts will help us help you in a more efficient manner :slight_smile:


Thanks, I’ll fill that out…

Also, I’m running Mega Crop nutes. I think I’ve heard you may have to add some cal mag. From looking at the Cervantes picture, it looks most like Mag deficiency.

  • What strain, Seed bank, or bag seed - WW x BB
  • Method: Soil w/salt, Organic soil, Hydroponics, Aquaponics, KNF - Soil, FFOF
  • Vessels: Pots, Grow beds, Buckets, Troths - 5 gal smart pot
  • PH of Water, Solution, runoff (if Applicable) - 6.5
  • PPM/TDS or EC of nutrient solution if applicable - 1298 in, 1896 out
  • Indoor or Outdoor - Indoor
  • Light system - LED strip light
  • Temps; Day, Night - 71
  • Humidity; Day, Night - 50
  • Ventilation system; Yes, No, Size - Big fan
  • AC, Humidifier, De-humidifier, - no
  • Co2; Yes, No - no

Thanks again!

1 Like

Did you recently transplant? It looks like her roots are unhappy for one reason or another. I agree, the pH is a little high for soil. If you can get it down nearer 6.5, it should help some. Also, make sure you’re letting the soil dry up some between feedings. Your runoff TDS seems a little high, too. Let the pot dry up, then give just pH adjusted water only until she’s ate some of that up. If the pH is off, no matter how much you pour in, she can’t eat right. Looks good, otherwise! :+1:


I would think same as the others, ph a little high. If you’re only running the mega crop at 1300 ppm in, you may be a little weak on nitrogen and high altogether. I’m pretty sure they have a nutrient schedule on their website, take a look at that.


I would drop that down to 700 to 800 ppm unless at peak flower. Your output TDS indicates it’s not using the nutes put in.

You may have an issue with calcium and might want to add some cal mag but FFOF should have everything you need until flower. I don’t use ANY veg nutes in OF. I still think there may be an issue with the roots. It very easily could be pot bound.


how often do you water and do you make sure she is dry first?

and you said a big fan is your ventilation. can you elaborate? is there a lot of wind on the plant?

and finally, what is the npk of the nutes?

i see temp/wind issues, overwatering, or nitrogen toxicity or any combination.


They look hungry and under watered…
Ph is for sure out of whack as well…
Dial in ph …figure out your time line and start feeding accordingly…
Then get your watering in check…
Best advice I can give …


You’ve gotten some solid advice from a lot of good growers. Get the ph down around 6.5 and see how she responds :wink::v::bear:


Thanks for the replies. Sorry for my late response, had to go to work shortly after posting and I’m too busy to get online.

Haven’t transplanted at all since going from the Solo cup.

I only water when they show me they want water - little bit droopy and the soil is dry at least to my first knuckle.

The big box fan is pointed at the floor area, not at the plants.

I didn’t start nutes until about a week before I flipped to 12/12.

NPK of nutes is as follows, and I’ve been going off the website:
Mega Crop (main nutes): 9 - 6 - 17 4mL per gal
Sweet Candy supp: 0 - 0 - 16 2mL per gal
Bud Explosion supp: 0 - 19 - 39 1.5mL per gal

I’ll see what I can do about the soil pH and will water with only pH’d water next time.

Thanks again and we’ll see what happens!


Hang some sticky yellow cards, just to see if any flying insects are around.

And I made a mistake about the nutes amount, it should be grams/gallon, not ML. So it’s:

NPK of nutes is as follows, and I’ve been going off the website:
Mega Crop (main nutes): 9 - 6 - 17
4g per gal

Sweet Candy supp: 0 - 0 - 16
2g per gal

Bud Explosion supp: 0 - 19 - 39
1.5g per gal

I also found this on the MC website:

  • If your plant leaves are light green or yellow , then increase your dosage of MEGA CROP to boost Nitrogen levels and increase green color.

I’ll see what happens before I add more though.

Thanks again!

1 Like

Your problem seems to be Nitrogen Deficiency and here are two pic’s showing just that>>



First off, some interesting, basic facts…

Your marijuana plants need 18 essential elements. They get carbon, hydrogen,
and oxygen from atmosphere and water. They get the 15 other elements via their
roots. These elements are sometimes grouped as major, secondary, and trace elements.
The groupings are determined by how much of each element is needed–some are needed
a lot more than others, but all are necessary.

The major elements are nitrogen, phosphorus, and potassium. The so-called secondary
elements are magnesium, calcium, silicon, and sulfur. Some people group these seven
elements as “macronutrients” because they’re required in larger weight amounts than
the remaining essential elements your plants need. Those are called micronutrients,
and they’re very important even though your plants don’t need as much of them. We’re
talking about iron, zinc, copper, molybdenum, boron, manganese, cobalt, and chlorine.

Until recently, silicon wasn’t even included in the essential element list, but modern
research on marijuana plants indicates your plants use silicon to build strong cell walls,
resist pests and diseases, and to create THC glands.

Nutrients problems most likely to reduce growth rate, THC percentages, and harvest
weight often involve nitrogen, phosphorus, potassium, and calcium. But problems with
deficiency or excess of any of the 18 essential elements is likely to cause serious
trouble for your marijuana plants.

How do you know your marijuana plants have nutrient deficiency or excess? Look at your leaves.
If they’re not lime green, upright, and looking like the perfect marijuana leaf photo
accompanying this article, your leaves are trying to tell you something.

But here’s a twist…it may not be your organic fertilizers, soil, or hydroponics nutrients
that are actually causing the problem. Signs of nutrient element shortages or excess may
merely be a symptom of the real cause of the problem. For example, low temperatures
interfere with nutrient uptake. So you can’t solve a temperature-related nutrient
deficiency problem by increasing your nutrients dosing…you solve the temperature
problem instead, so your marijuana plants can take in what they need.

The Right Amount of Nitrogen
Makes Your Marijuana Healthy and Green

Nitrogen makes up 78% of the dry volume of our atmosphere and plants need to
capture it if they want to grow at all.

No doubt you already know nitrogen is the big N in the N-P-K on your hydroponics
nutrients bottles, and it’s a big, important ingredient for your marijuana growing success.

Unless your plants are in the final weeks of flowering phase, yellow leaves
(especially lower leaves) are signs of trouble, and the troubles are most often
a nitrogen deficiency. It starts with the bottom leaves and works its way up until only
the newest growth is green.

On the other hand, if your marijuana plants are overdosing on nitrogen,
the leaves will be extremely dark green.

Either way, nitrogen problems mean big trouble for your marijuana plants because nitrogen is
absolutely necessary for plant survival because nitrogen is a primary elemental support for
protein synthesis, growth, leaf development, metabolism, and root health.

If you oversupply nitrogen, you get marijuana plants that are too tall, thin, and gangly.
It’s harder to get successful flowering from plants that have been overfed nitrogen.

If you see that the very tips of your leaves are yellow, that’s an almost sure sign of nitrogen
deficiency, which occurs most often during a fast-moving grow phase or when you’ve switched
to an improperly-configured bloom fertilizer during flowering. Many brands of hydroponics
nutrients do not contain the right ratios of nitrogen, phosphorus, and potassium, or they
contain the elements in forms that are not easily available to your marijuana plants.

These potential nutrients problems are especially harmful in flowering phase, when your plants
only have 12 hours to run their photosynthesis metabolism.

Nitrogen deficiencies first show up as leaf tip yellowing, especially on lower leaves.
Then it spreads to affect entire leaves, and moves up the plant. When you do research
on marijuana strains before you buy seeds or clones, take note of the strains that are
said to be heavy feeding. Those will likely want higher parts per million of nutrients,
and they are hogs for eating nitrogen, potassium, and phosphorus. In bloom phase, your
marijuana plants want less nitrogen, and more potassium and phosphorus.

The only time you tolerate signs of nitrogen deficiency is when you’re more than halfway
through flowering phase. During those closing weeks, your marijuana plants are focusing on
floral production so they sucks stored nitrogen out of leaves rather than doing the work of

That’s why you don’t need to add extra nitrogen (beyond the amount found in a properly-configured
flowering base nutrients product) to flowering crops after they’ve passed the midway point of
flowering cycle: excess nitrogen during flowering negatively affects bud development, taste, and aroma.

Fixing Nutrients Problems to Save Your Marijuana Plants

In later articles in this series, you’ll see a more detailed program for analyzing and fixing
marijuana nutrients problems but it’s important to understand a couple of things right away.
One thing to know is that organic or “natural” fertilizers often fail to remediate a deficiency
fast enough because they aren’t immediately bioavailable to your marijuana plants.

If you’re absolutely sure your marijuana root zone pH, grow environment, water, and other factors
are what they should be, and your plants are still showing signs of nitrogen deficiency in soilless
hydroponics marijuana growing, it almost has to be that something’s wrong with your base nutrients.

What are your remedies? If you’re growing in soilless hydroponics using synthetic hydroponics
nutrients, you have it pretty easy.

First, make sure your pH meter is working perfectly (or use the new pH Perfect base nutrients
that automatically buffer and adjust pH to the ideal sweet spot). Flush your
plants (I prefer
Final Phase or Flora Kleen), dump your reservoir, fill with reverse osmosis
water, and feed with
quality hydroponics base nutrients. When I say “quality hydroponics
nutrients,” I mean a reliable
brand of hydroponics base nutrients other than the brand you were using when
the nutrients deficiency

You can also experiment with slight up and down adjustments of nutrients
strength (ppm) or nutrients
water pH and see if that corrects the problems. For example, many of us
follow the dosage instructions
on nutrients bottles and end up with 500+ ppm during flowering. In some cases,
that’s too much, and what’s
really strange is that using too much nutrients can result in nutrient deficiencies.

So try changing your dosage 50-100 ppm in either direction, and see if it makes a
Try adjusting you pH from 6.2 to 6.0. Different nutrients interact with root zone
material and
water differently, so that you might get absorption of 12 elements, but the pH is
wrong for three
other ones. Even small adjustments in pH (unless you’re using pH Perfect base
nutrients in which
case it doesn’t matter), can affect individual element’s absorption.

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i knew it! nitrogen toxicity was my first guess but its rare so i went with over watering. flowering plants shouldnt be fed any nitrogen. and she is getting alot! i didn’t think it was underwatering. the leaf tips only claw at the edges. when prolonged underwatering is an issue, the leaves tend to sag more uniformly. hope this helps. stop giving nitrogen and get that ph right.

during veg i use sensi grow 2 part and in flower sensi bloom 2 part with big bud added. those 2 always keep my ph at 5.5. i test the runoff regularly.

Thanks for the info @garrigan62. It is kind of inline with what the MC site said. I’ve got a few days before the next watering, I’ll see what she looks like and decide if I add more or just do a water-only little flush and go from there. I’ll get a soil pH tester this week too and retest the soil. I’m not so sure I trust the results with the slurry test I did before.

Hey @JonnyPM, new grower here and using FFOF + MC. Just at the end of veg cycle for my ILGM Autos and am using Megacrop @ 1/4 tspn/gal, but might need to go up to 1/2 tspn/gal since the bottom leaves in my grow are yellowing! I also adjusted my pH to 6.5 so hopefully it’ll be ok. (RO water + MC @ 1/4 tspn/gal @ 195PPM). I think per the Greenleaf Nutrient’s site, I need to increase the dosage of MC to feed the hungry plants…I almost got some 0-0-0 CalMag, but I decided to wait until I try increasing the dosage since per GN’s site, MC should suffice. I think my pH earlier was also too low @ 6.17 so the uptake of CalMag in MC wasn’t there.

How did yours end up going? Sorry if I’m kicking this post back to life…