Please identify problem! +rep

Any ideas? Ph and ppm have been maintained to the correct levels. I am using coco on an ebb and flow table in pots. The only thing that has changed is I havent been running the heater and it gets into the 50s and the rez water is also in the high 50s low 60s. Also I just turned to 12/12 from a 400mh to a 1000hps. but the ones I left vegging it also happened too. I add cal/mag with my nutes been doing the same thing for a month and no problems. Only thing that has changed is temperatures

Heat stress.

Looks like light bleaching to me. You said you went from a 400W MH to a 1000W HPS; did you increase the distance from light to canopy drastically after you did that?

I had the same problem looks just the same on the right. But i had my post on it and got some answers sayn pho defiency and check my ph soil. Sooooo idk.

im pretty sure its the light. The inner top leaves of my scrog are the only ones with this bleach. the 1000 was pretty dam close maybe 10 inches i rose it to the roof so its probably a good 1.5 to 2 feet. also the ones i kept vegging also got the same thing cuz my 400 was now like 4 inches away i just had everything to close.

Around 20" is legit for a 1000W. Should clear things up.