Yellowing tops in veg

Hi all, not sure why my plants are starting to turn lime green/yellow and drooping. They’re in 1 gallon fabric pots. Using roots organic soil. Room is sealed with CO2

Temperature in room is 77-80f
Relative humidity is 60-65
co2 PPM: 700
Straight tap water
Feeding jacks 321 full strength every other watering.
Adding 3ml of calmag per gallon of water

I only water when first knuckle of top soil is dry. It’s been getting progressively worse. Some leaves are starting to have light orange blemishes/spots. Does anyone know what’s going on?

What are your runoff PPM and pH?

FYI: CO2 demands very intense light levels and high PPM to help the plant use the extra CO2. CO2 is best used in a hydroponic, high PPM, and a high light intensity environment. Plant gains are otherwise marginal.


Run off ppm for the majority of them was about 750-800 when I last tested a week ago but it’s not very accurate since every other plant had its own different range. Some were in the 600’s while some were in the 1000’s. Is there a way to test them all accurately ? Tested about 20 of them individually and sheesh it felt pointless because the results were so varied

Ph runoff was 6.1-6.2… I feed them at 6.5-6.8

Those numbers sound reasonable, but a bit low. pH is okay, but a little low as well.

I would ordinarily say wait for chlorophyll to fill in the green on the new growth, but if you say that it is getting progressively worse, then that may be a different story.

Other than that, I’d be stumped on this one. Step up your feeding by a third is the best advice I have.

@Myfriendis410 : any comments?

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Do you think it could be a root/potting issue? They’ve been vegging for almost 6 weeks now in those same 1 gallon pots. I transplanted a few and the roots aren’t rootbound yet so I’m stumped. Does it look like an overwatering issue by the looks of the leaves in the back?

Not feeding enough, should give full strength Jacks at every watering. Then you wouldn’t need the calmag either.


I would do as others have suggested and up the feeding.
But your plants do look to be ready for transplant. If they’re in fabric pots you won’t see any circling roots, but more root space will definitely help them out.
I would suggest a transplant and water them at about 6.7-6.8 to get your runoff to 6.5.

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Plants could also be pot bound and CO2 is making it worse.

Do you know what your DLI is? Very important with CO2.

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I add calmag because it looks like there’s deficiencies whenever I just use jacks. I hear calmag is always good for plants and it’s hard to overdose

That makes sense. Come to think of it I never see any circling roots like how I would with plastic pots. Thank you

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There’s plenty of calcium and magnesium in Jacks but only when you feed with every watering - not every other watering as you are doing, you are slowly starving your plants and that is what is causing the deficiencies.

See how my plants look with Jacks every watering and zero calmag (no deficiencies here):


I do not. This is my first time hearing about that. Do you have a link to an article that can ELI5? haha

Thabk you, your plants look great. Are you growing in soil like me though? I’ve been very careful about not feeding too much nutes because I’m in soil

I’ve grown in almost everything, was a soil grower for 30 years and still grow my clone mothers in soil, those plants pictured are in coco but that does not really matter. Your soil ran out of nutes a while back, now is the time to feed with every watering, do that and your plants will look great in a week.

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Thank you sir. I’ll try that and report back in a week


My clone mothers in soil get to looking like your plants when I cut their feedings down too low to slow down their growth. After a few waterings with full strength Jacks they come back very strongly.