Top leaves yellowing

Hey, looking for opinions on my top leaves yellowing. This is a Strawberry Kush Feminized with about 4-5 weeks left (I think). PPMs are on average 700. Water replaced last week and I generally use about 4 teaspoons of Cal-Mag when feeding/water replacement, and equal parts of General Hydroponics Flora series trio. PH is always 5-6.
note: another plant is pushed up next to it right now if that looks odd

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:point_up_2: too low Growmie. Need that around 1000-1200 for soil.

:point_up_2: too low for soil. Range of 6.2-6.8 with 6.5 being the sweet spot.

If you’re in Coco the PH is good but still need the PPMs at 1000 :love_you_gesture: are these run off numbers ?


This is hydro / coco. So I am going off someone else’s recommendations for this point in the grow as I am a first timer. You think 1000? Do you think that could be part of the issue with the yellowing? And If I truly have 3-5 weeks (somewhere in there) should I bump it? I had read to start backing off about 2 weeks before harvest to drain out nutrients.

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She looks nitrogen hungry and possibly a magnesium deficiency. Yes on the 1000 PPMs and your PH is good, for my coco grows I go to 6.0 during flower and straight water feed the last 2 weeks. 1/2 teaspoon of epson salts will feed magnesium and sulfur :love_you_gesture:


OK Thanks! I had gone up on cal-mag a few weeks back when I saw some yellow down low. It cleared up and I backed off of it. I will bump it back up, get PPMs closer to 1K and get some epson salt - thanks for this tip.

I always worry when I see a broad stroke pH like this. Hydroponics is one of the few things I feel is truly pH sensitive. How are you measuring pH to get those numbers?

PS, the sweet spot is 5.8 vegging, allowing it to raise up as high as 6.2 during flower, occasionally adjusting back to 5.8 so she can get vital micro and macro nutrients. OG is on point with his advice. :v:


i use test strips. i tried a meter but even after multiple calibrations i could not get consistent readings.
open to suggestions by all means

Test strips are not reliable. Get a blue lab or apera meter. Very important to get your runoff numbers and puts your mind at ease. During flower, they like potassium and a little less nitrogen.

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My sentiment exactly. I have BlueLab, which is pricey but it’s calibrated for 30 days easy and often stays accurate much longer, I just know they recommend recalibrating once a month just to be sure.

Apera is the best budget brand that remains reliably accurate - the pH 20, I think. Should be right around $50 and will last a lifetime.

I use pH tester drops for my aquarium and check it against my BlueLab all the time. Drops and strips are okay for ballpark (between 6 and 7, for example) but they don’t nail down the specifics to 0.1 or 0.2. For hydroponics, that bit of accuracy is the difference between your plant using what you feed her and her just trying to make due with what she can provide for herself.


Thanks. Runoff? This is hydro. Is that a thing here? Anyways, I will look at Apera.

Thanks, I will look into them.

@beachglass , @Graysin - Do you know anything about Atlas probes? I ask because it is my intent to do some automation and they are the PH probes I was looking at for this. I am a bit of a ways from this so I will probably pick up the Apera now. I am hoping my automation will help me do a better job of controlling nutrients and PH.

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I don’t know much about Atlas except that I used their pH up/down for a while. It seemed fine.

BlueLab makes a controller - it does pH and PPMs, and can automate dosing (adding more pH up/down or nutrients as needed). It’s like $1250 USD but honestly that’s not a bad price for extremely reliable. They also make the Guardian, which is just an in-line pH/ppm monitor rather than a controller, but it’s also $350 instead of $1250 so there’s that.

so I got my Apera. calibrated last night and did initial test and it was way off from what i expected. going to retest in a bit to make sure. i think they may have calibrated before sending as everyone of my test chemicals had been opened and was 1/2 gone. the storage solution was gone. or i got a used unit - probably this. have to decide what i want to do there.

i do have another question on yellowing. since i have been using these strips for a while, my guess is it was at least close but maybe not. is it possible this is from being too close to my light? top of plant is about 15" from HGL 225 and it is cranked full intensity (was told to for flowering).


Let me grab @dbrn32 for lighting and yellowing tops. I’m just not that familiar with all of HLG’s fixtures, sorry :sweat_smile:


This isn’t ridiculous, but maybe a little close if it just happens to be a light sensitive plant.

There are a number of things already noted here that should help you.

Is it hydroponic or in coco, or you have both? These are definitely not the same, just treated similar in some aspects.

I have a baseline for coco around 950ppm. This doesn’t mean that’s exactly and all i use, need some flexibility for environmental swings, different plants, etc.

I agree with this. In fact i would say if you can keep around 5.8 your entire grow shouldn’t be much to fuss with ph. Letting a hydroponic res drift up a small amount is tactic used by many.

They leak, it sucks but happens. Not sure on current pricing but amazon has some kits of larger bottles of storage and calibration solutions. If not Contaminated should last you a very long time.

One single straight watering without nutrients or being ph’d can set mature plants in coco astray. If your ph wasn’t pretty close for extended period of time I would expect to see some issues.

Curios mainly on the hydro/coco question, will likely have some additional feedback with your answer.


Sorry, I mix terms and usually confuse these. I meant to say hydroponics and my medium is : 4qt Hydroponic Clay Pebbles, 8mm-12mm, Toypopor Natural Organic Expanded Grow Media for Hydroponics, Drainage, Decoration, Aquaponics and Other Gardening Essentials : Patio, Lawn & Garden

So something like a dwc system then? Dissolved oxygen is extremely important in something like this and is often an issue. Need lots of air pumped in and water temp to stay around 68f.

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correct, DWC. i have an aerator. i do struggle occasionally with water temps. i actually got a chiller for this but have yet to implement - trying to decide on how i can best implement RDWC in my tiny closet.

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Use of a remote res outside of the closet a reasonable solution? This could give you an easier access point to test and change solution.

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Great minds… This is my desire but I have some logistical issues I need to deal with. One being the wife and getting that approved. Another was how I pipe it in - which would most likely require a hole in my wall. Right now I am running two and they are 5 gallon buckets so I am sure you know the water/ph/nutrient challenges that raises. Once I get through this one I hope to have a viable solution for RDWC. Thanks for your help.