its coco so i guess its considered hydro. the coco is gold lable and the perlite is unknown. its an indoor set up we have multiple strains, chem dawg, kryptonite og, tahoe og, acid and green crack. they are 4 weeks old we jus flipped them 3 days ago but this problem has been on going. we have 2k raptors and they are about 2-3 feet from the light we water every other day expept when we fush we giv it an extra day to dry so a total of 3 times a week and all our water is ro water. im not sure how much npk but the last watering was at 1189ppm and ph'ed at 5.8 , daytime temps are 73-78F 50% humidity and night 65-68 unknown night time humidity. they are in 5 gal smart pots and the only bug i seen was a gnat here and there not nothing big else.
at first glance, it looks like over feeding. the main plant in that pic looks kinda toasty. I see other leaves in the background that appear to be a little toasty as well
1200ppm is pretty high. im sure maybe some of them can take it but the old adage "less is more" stands true w/ feeding coco. my perpetual 4k flower room runs no higher than around 850ppm (.5 scale)
also, running plain water through your coco is kind of a "no-no". it may, or may not be contributing to your problem. personally, ive seen guys do this and not have 1 problem and visa versa. something to keep in mind though
I see your running Co2 and your temps are pretty ideal topping out at 78*. I'm sure that's the ambient, but what's your temps under the hoods.... at canopy level?
a second glance makes me think it could be a transpiration problem, check out the link