Hmmm,,,,Your creating more problems by leeching (flushing) so much. Plants in the "green" are high N and kinda look over watered BUT, you say you don't water till dry - so high N it is!
The plant on the left is having P trouble. By the necrotic spots. I'll say it's a pH problem brought on by the pot being wet/damp for too long a period of time.....this is from your "flushing" as extended periods of wet will keep the pH low too long. This cuts availability of P (and other things like Mg and Ca - those are starting showing too).
Normally I would say that it's a too much P thing as you most likely started bloom nutrients too soon - BUT the necrosis in the leaves say "not that"....pH !
For that plant = pH your in going fluids to 7.0 and use them. At this point in the run, it can still recover enough to improve the yield of it. The others = reduce the N and continue with no "flushing" and see a pretty quick improvement....The leaves on that yellowing plant will never "recover". It should stop the progression of others following. It will take like 5-7 days for this to happen...
I like to water a metered amount everyday at lights on! This does 2 things for me.
1: It supplies more 02 to the roots =
good thing!
and
2: It allows for a more natural pH swing in the soil. = Makes the nutrients available at peak rates*.
* Soil will drop in pH around a whole point when you water. As the soil dries back out, it rises back to it's "normal" level.
Here is a pretty good Nutrient availability chart for pH levels - first one is hydro and the other is soil..
Good Luck!
