No it's just happening to that one. My ph is good. Usually around 6.3. I uped my next batch of water to 6.5 since I've been reading 6.5-7.0 is optimal. My backyard gets hit with direct sunlight from 7-7. I have been slacking on my feeding but started giving them fish and kelp fertilizer along with an organic 5-4-2. They seem much happier and greener ever since.I didnt know you had more than one. this is a condition.
according to rosenthal this is a sign of reveg.
I suspect a ph issue, assuming all of your micronutrient needs are being met?
how many hours of daylight are they getting?