extreme cupping on top half of plant leaves, yellowing and crisping? Black Dom?

Gonna give this a shot, I have a few black doms and within the past few weeks the top half of the plants have cupped and curled downwards. I thought at first maybe it was my ph was off, but i have another strain or two and they don't seem to be affected (maybe the other strain is more tolerant of varying ph?, Blue dream). I'm thinking some kind of nute burn, but the bottom half of the plant seems to be normal with minimal stress. The upper leaves are starting to crisp. I am in soil (happy frog), using canna terra products, (i'm in veg), ph about 6 although i am using the old method of using the take a sample with a dropper method, so i can't measure my ph after i add nutrients. I've used this method for a long time and never had problems. I've tried flushing them out? I'm just wondering whether maybe the strain is super sensitive or i'm missing something.

any suggestions would be appreciated

couple more pics same plant

looks like the nitrogen claw, and why cant you pH after you nute your water?

Are they really close to the light

yea i was thinking it was heat maybe what are your temps?

I hit mid to high 80's for a week or two, I was using t5's so i don't think they were that close to the light? I can't ph after because i don't have a ph meter. After I add nutes the color gets distorted so i can't tell my ph. Maybe heat stress but i thought they would of recovered by now, that was like 3 weeks ago. the rest of the room was unaffected.

i was thinking of topping all the really stressed leaves? think this is a good idea? I don't think they would recover. I'm still in veg and want to give them 2.5 more weeks.

You really need to be checking your PH and PPM's correctly, or your really just shooting in the dark. Your pics are not great, but it does look like your nutes are too hot. Also, dont cut anything off the plant, that will just create more stress that you dont need right now. They probably wont unclaw, but so what, they can still do some work.

At this point, you will probably need to flush and start fresh with a lower dose of nutes.

Looks like Heat Stress to me?.....try cooling it down in your grow area/box/cab!
Good luck bro!

yea upon further inspection its deffinately got to be heat. im sure of this now because the lower half of your plant is okay. tie your plant down away from your light, pronto before you get worse damage.

and deffinately dont trim you r leaves off.. they might not be pretty but you still need them