Heat stress @ 77f ???

So I'm running a clone right now and it seems to be suffering from heat stress... But the temp lights off are 68/70f and lights on are 77/79f. I can't see how heat stress is factor. I admit humidity is high (65-80%) but in veg that shouldn't hurt it. Also my lights (hlg65) are 24" above. I included some pictures to help explain. Thanks for your help.

Medium, soil, ph, nutes? More info the better we can advise.

lime73 said:

Medium, soil, ph, nutes? More info the better we can advise.

Click to expand...

Soil, ph 6.8, seaweed extract and calmag. 4 weeks old.

Did its soil hit a dry spell, did the stems go purple around the same time. My guess just drought stress not heat but leaves get hot when low on water.

There could be many possible reason why your leafs stems are Red, and your leaf margins are clawing, not to mention the waxy looking new growth. As 2Hearts said it could be stress. What kind of stress could be a few things. As Lime73 said "The more info the better. What does the description of that Strain you're growing say about how the Strain grows. This is an offsite link. Go through each of their 'Causes", and see if some might apply to you.
What causes red stems in cannabis plants?