need help identifying growth problem
I've got some plants that are initially growing great, but when the second set of full leaves come in they'll be very yellow. Eventually (2-3 weeks) they'll start developing white patches and the plant will stop growing.
My setup is:
- maxigro nutrients, no EC meter but mixed to the "proper" strength, I've tried as little as 50% with the same results.
- drip system, on 15m off 15m
- 400w HPS a couple feet above the tops (~2500 foot-candles at the plants)
- 24h light since it's all vegging
- PH is ~6, maybe 5.8-6.0. I'm using the General Hydro color based test kit, so it's not very precise.
I've had the problem with tomatoes and green beans, but everything else seems to be fine: a few types of greens, carrots, parsnip, and okra. I also have a bell pepper that looks fine, but its a small plant and barely has the second set of leaves. I have two watermelons that are yellower than they should be, but they're growing fine.
The older leaves will pretty much stay green. The veins in the leaves will be pretty much equally yellow. I've added some Iron recently thinking that might be it, but I'm not really sure and it's too early to tell if that's the problem.
Some pictures can be seen at:
Any help will be much appreciated, thanks!