guidance needed (yellowing and blackening): pics inside

I posted a week or so ago about yellowing on the bottom leafs, and was told that they typically do that naturally, but this has spread upwards. I had a PH problem in the beginning, so I went ahead and did a flush this morning.

Plants are about 5 weeks old (starting at seed).
I'm now using water with a PH of about 6.6-6.7.
I just flushed to runoff of PH 6.5.

I'm using 33% light warrior, 66% ocean forest.
Lighting is a 400w MH for veg.
Temps in the room stay 72 during dark and 78 during light (18 light, 6 dark).
Watering every 48-72 hours (when the solo cup feels almost as light as a solo cup of dry medium)

Nuting with 1/2 strength FF big bloom and grow big, about twice a week (every other watering). Looked through the plant problems and my guess was K, but it was showing signs of a little bit of everything it seems. Like I said, I decided to do a flush, just in case. It seems like a lot of people do that around week 4-5. Any other suggestions or guidance would be good--I'd like to know if I'm on the right track. I plan on transplanting to the final pot in a few days. The biggest plant is about 10".

What was your ph before? Changing ph in a day can harm your plant, so always try lowering your ph throughout a couple of days.And yes, it is showing a sight deficiency in p too, i can see the stem turning purple.20-20-20 ferts are good , it will give your plant what it needs and may clear up your def. Problems.

Why do you still have your plants in solo cups after five weeks? Are they still that small? I would suggest an immediate transplant into larger pots.

They are about 8-9" tall. I only took a picture of the bottom leaf. I am transplanting tomorrow. I've seen much larger plants in solo cups than what I have, so I was holding off. I'm waiting until dark cycle to do the transplant.

Why on earth would you wait to transplant in the dark cycle? It's supposed to be dark in the dark cycle, and it's sure easier to work in the light.

Just because some people keep their plants in solo cups until they are big does not make it a good idea... Some people smoke crack, too.


Just sayin....

I have a green LED headlamp that doesn't disturb the plants during their dark cycle, but I really meant towards the end of the light cycle, primarily because the rootball wouldn't be so wet when I did the transplant, which I did this morning.

The good news is that the plants were only mildly rootbound. There was a small amount of looping on the very bottom, and not anywhere else. We'll see how they like their new home (100% ocean forest).

Gotcha. That makes more sense. I think they'll like their Ocean Forest. Did you add some Perlite and Dolomite lime? Very helpful for Fox Farms soil.

flush, transplant and maybe try a little stronger nute solution...
thats what i'd try

Thanks PJ--that's exactly waht I've done. I plan on doing a full dose of GrowBig and BigBloom whenever they require the next watering. I expect that, due to the larger pot they are in now, it may be another couple of days before I have to water again. So far so good on the transplant and flush.

If those leaves were touching the soil before, then they're gonna do like that... Just trim them off, and transplant into bigger pots. You may want to add some dolomite lime to the new soil to keep your ph in check.