Is this Heat stress? or somethin else

Hey ...my girls where looking fine last week , and now im seein, yellow tips, and its on most of em, worse on others, like it spread around the upper leaves leaving just the middles the normal green. also 1 strain has most leaves curling upwards, now. def looks like a problem. I lifted lamps up another 1ft. They where about 12in from the canopy be4. 600hps. Other problems i was thinking , was my tap water. very high ph where im at like 7-8. Ive been tryin to lower it, but the vial testers suck..

so wuts my problem doc??

yea id say its heatstress man. peace

shit i double posted this thread, heres the other w/ better pics >>>



https://www.rollitup.org/marijuana-plant-problems/184221-heat-stress-somethin-else.html