Heat stress most def, just need to have better exhaust for moving the air out the area.
CFL's too close, definitely not !
They have to be that close due to weaker lumen output, but the plus is the less heat to the touch, so put them back where they were.
Their growth has been stunted by the ambient air temps being too high.
Not enough transpiration in the leaves, so the stomata are basically being choked out.
At 5 weeks veg, those plants should be no less than 12 inches tall, in any hydro set up that's fairly dialed in environmentally.
It's not too late though.
Drop all pertinent info about your set up.
Lights, watts, qauntity, fans used, intake (passive or not) and exhaust, rez temps, etc..
Lots of us on here willing to help.
Good vibes to you and your grow.
p.s. What kind of medium is that ? Curious.
