I'm sorry, OG - I didn't find your journal until lately, but I just finished reading through it. You had me puzzled until Jul 27th.
It looked like they were getting too much of something - burnt, overfed. But it was clear that you had read the instructions and it seemed that everything was "normal", despite the consistent yellowing and poor vigor. I kept looking for light stress, trying to see how much they were getting.
But no, that was fine. You're an experienced grower, so no point in wondering about stupid stuff ...
Finally, you let slip that they hadn't gotten any clean water. At all.
Oops!
And in one gallon pots, besides!
I was getting embarassed, wondering what the heck went wrong - you didn't get much traffic, so no one really studied and asked you stuff. Ack! We can do better than that!
And then, bingo, the light goes on. Duggan gives
two clean waterings between drenches in his big 26 gallon pots. And you were also spraying DeStress every 5-7 days, which is too often to keep up for very long. If one of us had been watching and known, we could have halted all this damage sooner. I was even wondering if it was toxic water, but then I saw that you have a 5-stage R/O, so nope.
They got overdosed - consistently.
I have an instinctive suggestion. If anyone disagrees, please pipe up. Assume your biota have gone lazy and aren't inspired to eat rocks and reproduce n such. So they'll need a couple weeks to wake the F up. Tea would help, as would Transplant, but not as feed, but more like tweaks, microdosing, y'know? You'd like to point 'em in the right direction but make them do the work. So maybe give them a full dose of Tea in the next watering - just the Tea measure, then follow up a day or two later with a 1/4 dose of Trans. Watch what happens for a few days. Adjust accordingly, trying to encourage the biota to fall in line, and the plant to get the exudate/biota linkage back in shape.
They should green up a bit at the top. I've had more than one plant end up looking like yours, and when they recover, the new growth is good. The old fans will probably all go south though - been fading too long. They're only really necessary as sugar factories after growth stops though. The plant will replace what it needs.
Be wary of GE in this condition. I've had better luck doing Trans drenches when they're crispy like this.
Can't think of anything else right now, except, I'm sorry we let this happen.