Support ticket // Yellow & purple leaves during flower

Strain; 2 plants, Girl Scout cookie extreme auto and amnesia haze, both ILGM.

Both plants growing in FFOF with 40% perlite in 5 gallon cloth pots sitting on grates for proper drainage.

Aerated tap water PHd to 6.5 after nutes.

Judging by weight the plants are watered every 3 days. Every other watering nutrients are given, so every six days or once a week. On the off day tap water and 5 mL per gallon of cal-mag is given as supplement.

I’m using fox farms trio for nutes.

Half nutes were given at first and the plants took it well. I then got overzealous and gave full strength 6 days later. A few days after that the leaves yellowed a bit and showed signs of burnt tips. After a watering of just cal mag the next feeding 6 days later I used only 1/4 of recommended nutes given as precaution. Leaves have not improved, only become more yellow in general with some purple stems and purpling leaves.

Indoor tent 4x4, spider farmer SF-4000 and SF-2000 (over other two plants in tent) 6” AC INFINITY ventilation with charcoal filter, x2 6” intake fans and large canopy fan.

7 weeks out of soil, 3 weeks into flowing

Humidity 40-55%

Temps 72-80 F

16/8 schedule

I’ve been pretty diligent, but this is my first grow.

The plants are growing well, buds are getting bigger and denser, just discoloration of leaves. I’m not sure if I have the nutrients dialed in. I’m concerned its either a deficiency or an over feeding, obviously knowing which one is very important though, and I’m looking for expert opinions please.

Added some pictures, let me know if you need specific pictures or close ups. Thanks in advance.


Hello :v: Do you have run off #'s ? Are you following the fox farms schedule? and doing the flushes?
Let’s tag some help @Myfriendis410 @MattyBear @Covertgrower


First it would be good to have runoff TDS and PH. FF recommends flushing at different intervals while using the trio. I suspect you have an excess of P with a lack of Calcium and magnesium.

So first thing would be to flush using three times the pot volume and capture the last ten percent to measure. You want a PPM and PH measurement. I would suspect it will be well over 2,000 ppm and PH around 5.0. If you don’t have a TDS meter it’s time you order one.


@GreenJewels @Myfriendis410 the first flush is scheduled for Tuesday. I just watered with cal mag only yesterday. I plan on using FF sledgehammer with flush. I will acquire run off values then.

I am following the FF schedule. I started with week 5 on week 4 as I planted in ocean Forrest. The schedule shows a flush between week 4 and 5 however I didn’t do that one as I had only fed once. I was planning to flush on my next watering between week 7 and 8. Week 4 and 5 were half strength, week 6 was full strength, this is when discoloration began, week 7 I only did 5-5-5 ml/ 1.5gal BB, GB, TB Followed 3 days later by yesterday’s 1.5 gallon per plant 5mL cal-mag watering.

Also three times the pot volume may not be feasible in my situation. 15 gallons per plant of PHd, aerated water is hard to come by, plus I have nowhere for the runoff as they sit in small drip pans.

Using sledgehammer makes it so you don’t have to flush with lots of water.

A forum member recently wrote to fox farms customer support and they said to just mix the sledgehammer as directed and apply it. No need for additional flushing.


The only problem is you won’t be able to get any meaningful data on the state of the medium.


I guess it depends on whether the goal is to flush out the salts, or lower the ppm’s.

Way too many beginner soil growers get the idea that they need to flush their soil to below 900 ppm before they can feed. They flush all the nutrients out of the soil and end up acting as if they are growing in coco.

If growing in soil and your ppm are below 2000 then I think you are doing something wrong since the beginning ppm in ocean forest soil is 2000-3000 or even higher. You don’t have to deplete all the nutrients in soil before feeding them, especially if you want to push the lights.


@GreenJewels @Myfriendis410 I flushed 1 gallon using 10mL/gallon as directed of sledgehammer ph’d 6.5 followed by 1 gallon aerated tap water. I emptied the tray after the sledgehammer runoff and tested the ph and TDS of the last bit of runoff from the fresh gallon.

Both plants had identical test results.

PH 6.0 and my TDS Meter only reads 3 digits, or in the hundreds not thousands but it around 400 PPM According to it. So maybe I AM doing something wrong here?

Update, more yellow at the bottom of plants and purple on sugar leaves and bud leaves. Also noticing some purple striping in both plants stems.

Is it possible the yellowing I saw before cutting down on feeding concentration was the beginning stages of hunger rather than signs of nutrition burn? And then cutting down the food has now worsened the hunger, and it’s presenting signs? I’m possibly starving my plants thinking I’ve over fed them?

With that being said, using sledgehammer is it ok to feed right after flushing? As in same day? Thanks guys @Covertgrower You’ve been helpful in my other thread I thought id tag you as well


That’s pretty low, you need to raise your pH. When I used ff nutes and soil, my pH always dropped in flower. Eventually I started to pH my water around 6.8, depending on my previous run offs. Here’s a reference chart


Which ff schedule are you using? Your ppms are low, they are definitely hungry but they also need the PH up closer to 6.5 to absorb the nutrients.
The 1st schedule is the schedule I used in my first grow. Then I gave sledgehammer 1ml with every water. As time and grows went on I added more ff nutes ( the dirty dozen) and then I used the second pictured schedule. I don’t use ff nutes anymore though.
The second schedule pic is also adjusted to the correct ppm scale. That’s another bag of worms I won’t open to far but, ff uses a different ppm scale then most meters are defaulted to. Regardless, you can see the ppms need to be higher

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@GreenJewels do you recommend a TDS meter?

I’m also using the schedule you said that you use. The last picture. I started all three nutrients or week 5 on that schedule, on my 4th week above soil starting around 1/2 recommend dose. I’ve attached a picture of my feeding and watering schedule. I started noticing browning tips and yellowing after the full strength feeding on 10/15.

I also attached a photo of affected leaves I cut from both plants.


No, your TDS meter is fine. Once you get the pH up, they can eat what you’ve fed them. Anytime I flush I follow up with a 1/2 strength feed. Like you, I did Calmag on water day.

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Thank you. Good advice and helpful charts. I’ll feed them later in the day and we’ll go from there. Hopefully the flush does the trick and no more yellowing.

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Usually there’s a tiny X10 indicator that shows up. It’s hard to see: take the reading and put the meter on ‘hold’ while immersed then remove from liquid and read result.

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Ahh I see it now. Unfortunately was not lit up so I think my PPM is actually 400 :grimacing:

If you are sure your runoff numbers are that low it’s time to supplement. A concentration of around 1,100 ppm of bloom nutes with a bit of N and some cal mag ought to set you up.

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I fed them half strength recommended dose after flush yesterday.

Dumb question, are feeding ppm reading taken of the mixed nutrients prior to feeding or of the runoff after feeding?

If anything good came out of the discoloration, it makes for cool pictures :man_shrugging:


Both. Runoff numbers can tell you a lot about what is happening with the plant in the root zone.


Yellowing is getting worse even with full strength FF trio and 5 ml cal mag with every feeding. Yellowing points towards nitrogen deficiencies is what I’ve read, but both big grow and tiger bloom have plenty of nitrogen. I even gave all the plants 15 ml / gal tiger bloom rather than the recommended dose of 10.

The ph still comes out a bit low with runoff but between 6.1-6.3 on the last watering. I’ve also been using water ph’d to 6.8 as an attempt to increase soil ph.

I’m at a loss. They are 9 week old auto flowers, started flowering around week 4. The GSC and Amnesia haze have great colas and if I have to chop them a bit early I will to salvage them. Tricomes are mostly cloudy with maybe 10% amber on the main colas.

The other two plants are the same age but obviously behind in growth and maturity, but they’ve started yellowing as well. Ugh.

Any suggestions?

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From what I have learned here, if you’re almost ready to harvest, low nitrogen is not a bad thing. You can think about harvesting mature buds and leaving the others to get more of everything and continue to grow.

Get that ph up!! They are not eating. Below 6.5 is never good. They can’t eat.