Thank you so much for taking the time and the various answers
@Terp1!
I just realized I can post questions directly in the diary. Next time ill do that.
That photo is from last night. But its been 2 days like this. When the light comes up the leaves are still down.
Regarding PPF, im not sure, I don't have a PPF meter yet (ill get one). I read online that 400 HPS should be at 40cm from the plant. I left it at 80 cm because it was heating quite a lot (above 28 celsius), in fact the seedling stretched a lot so I believe they are not receiving enough light. Thats why i thought this was maybe due to overwatering (and not excessive light).
Ill increase the humidity and see how it goes!