I saw the photos in your journal, but did not have a chance to reply.
I see superficial damage to the epidermis, of the top-most leaves. I see a bit of leaf taco. You mention the plants are not stretching upward.
All of this COULD say excessive light intensity.
Some of this COULD say temperature.
Say the opposite were true. What would happen if these plants were NOT getting enough light ? They would be super tall and stretchy. They would be pale in colour with small leaves.
A leaf will taco like that in response to to swings in temp., or extreme temperature, in itself. Whether it be too cold at night, or too hot during the day
The leaves that are showing damage are horizontal.
Are the leaves in the lower canopy showing the discoloration? Or just the ones closest to the light?
The growing tip is somewhat more immune to light burn, as it is vertical.
** I see
@DopeDaniel , as replied while I was composing.**
Looks like the two of us may be thinking along the same lines. And the advice I was about to give would be the same.
Raising the light up I bet would stretch them up, if nothing else.
Topping, if you haven't already, would encourage the lower branches to make their way up to the canopy crown