Heat Stress?

Im having my father in law grow plants using hempy style so that I can make RSO for his cancer. Just went there yesterday and about half the plants are curling up really bad, but only the top set of leaves. They also have tiny yellow spots on the lower leaves. I had been using .625ml/gal of DynaGro but just upped it to 3.5ml/gal because I was seeing deficiencies in my own plants using the same feeding amounts. Mine looks perfectly healthy but his are looking like crap, again, just half of them. Does this appear to be heat stress or lack of water? The affected plans were int he back of the tent so they are kind of hard to get to so maybe they werent being watered enough. Also, these were replanted about a week ago but just saw these symptoms yesterday. It appears the lower sections are starting to produce new leaves and look otherwise unaffected.

Heres some pictures.

Could be heat stress. What is the temp directly under the lights?

Was reaching 86 next to the plants. I have since adjusted things and am keeping it between 76-81. I also read about when upping the nutrients curling may happen but this is only happening on the upper most leaves. The bottom ones look fine and theres no burning on the tips. Im leaning towards heat and possible lack of water. Im not 100% since Im not taking care of them. I did take two of the worst ones home to see if I can correct the issue.

Nute burn happens on the tops of the plants first, usually the younger growth. The thing about heat and nutes is that when the temps go up plants are more susceptible to nute burn because they take up more water and the nutes with it.

86 isn't too high every now and then but for extended day cycles without someone topping off the res the plant will deplete the water level and cause an increase in the nutrient solution's concentration/ppm.

The plants pictured here aren't so big yet that this will happen quickly but it will still happen and they young are enough that it won't necessarily take huge swings in ppm concentrations to have an effect.

Well now that I wrote all that I just double checked your description and realized you are hand watering. 86 everyday without co2, 86 is the perfect temp for co2 supplementation, and lack of watering could definitely/likely be your problem.

Edited for grammar

thanks, i think its the combo as well but just wanted to get some opinions.

Just checked again today and the pots were already half empty! They are drinking tons of water. If I hadnt come the previous day they would definitely be out of water today. Just told them to up it to 16oz a day for now to see where that gets us.

Have you tried to get your temps down? The quality of your buds will really suffer at 86, 75 is where you want to be. Or you could keep your temps there and add co2

Yes, took care of the temps. They stay around 81. Put a 400 cfm fans instead of the 240cfm. Also have them opening the garage every few hrs to get rid of the heat. Pretty soon I will be venting the exhaust into the house to keep temps down in garage.

He has the hot water heater out there along with insulated garage door and is in a town home so it's always relatively warm.