What is THIS?

It's moving up my plants. As one set of bottom leaves die, it moves up to the next set of older leaves. However, I am still having new growth below the larger fan leaves that are yellowing and dying. Please help, I've come so far to lose them now.

Looks to me like it could be overwater, nitrogen deficiency or overfert, or the pH is off, but really if you said the pH might be off for every person asking a question on here you wouldn't be wrong...the pH being wrong or fluctuating rapidly can cause every symptom you can think of just about...lol.

So, what lights do you have? What soil are you using? And have you given them any nutes? If so, how much of what kind with how much water how often...? If not>>>then they need some...

How old are they...I see what looks like flowering..so is this plant in flowering? The leaves don't look too terrible to be totally honest...and sometimes in flower the lower leaves will die off, and I see that your cotyledons are still there and visible, so you really haven't lost too many leaves...but you say it is killing higher up leaves as well?

some pictures of the whole plant would help me out a lot to tell the truth...I know it is annoying to take pics of flowering plants but for real get them somewhere with a more natural light spectrum and let's see what is going on here...I know how this feels, seeing something happening and perhaps what you have tried is not helping or you just have no idea what it could be...

I might not know either, but there is a better chance that I might if you show me some correct colored pics of the whole plant...ooohh and answer the litany of above questions...medium, lights, water? the basics...

i wouldn't worry about the leaves on the very bottom ....as those are usually the first to fade and die off....once plants are bigger.

as long as is not all over the plant.... they are fine.

Hi missnu...thanks for the reply. They are 2 months old. Were under flos until 2 weeks ago and now under HPS 18/6. They've been in Happy Frog since seedlings. Began using FloraNova Grow 3 weeks ago at 1/2 tsp per gallon. I water about every other day but only with signs of water need...like slight wilting and light pots and soil dry more than an inch deep. pH automatically goes to 6.5 once the nutes are added. I have great air flow (intake/outtake). Temps fluctuate from 75 deg F to 90 deg F. I've had a cool mist humidifier on them 24/7 that keeps the RH to around 30-40%. They are about 24 inches tall now and I was about to take some cuttings, but was afraid the problem would spread to the clones and kill them all.

Once the yellowing began 2 weeks ago, I asked our local Hydro store owner (been in business for 30 yrs) about the yellowing and he said to up my nutes to 1 full tsp per gallon. Which I did, but it has not stopped the yellowing.

Oh and those are not cotyledons, they are the first set of leaves that yellowed and died. The cotyledons were removed when the were about 6 inches tall and died off. This has moved up the plants and is now on the 3rd set of leaves. I'll post more pics tonight...just takes a little while because my internet is slow.

P.S. This is happeneing to my smaller plants, too. I get pic of those, too. Again, thanks for your help ..!

Oh missnu, did you notice the curling up on the yellowed leaves? I've read Magnesium def so I did the epsom salt dilution in a gallon of water. All this did was draw up the leaves that were yellow at that time to unrecognizable little yellow wads within minutes.

how tall are your plants? is it yellowing only on the bottom, of the older fan leaves?

Hi lime73, the prob is...the yellowing is going up the plant. And the stems of each yellowing leaf is reddish purple.

This pic is of a whole plant, which is typical of what they are all doing right now. Was topped at 4 weeks.

its fine

see its only on the very bottom leaf of your plant...your plants are healthy

here is one on mine...bottom leaf rest is healthy

The yellowing is moving up to now the third set of leaves. Can you see the red/purple stems?

Thanks lime73 but why are my smaller plants (one foot and some 6 inches tall) doing the same thing. I wouldn't think too much about this if it were only on my larger (24 inch tall) plants. But all the yellowing started at the same time.

yes the very bottoms will die off as plants get bigger...its only a 3 spear leaf , nothing to worry about...seriously....so that would be ok if it dies, and it will fall off.... cuz its on the bottom....not much light down there and its normal...trust me!

the person who tells you its a N deficiency,will be wrong and you will just end up overdosing your plants if you add more nutes...to try to correct something that is not needed.

got a pic of the smaller ones?