Light burn on seedlings?

some look like nute burn. possibly from hot soil with too many nutrients in it. they should keep going tho and be fine and eventually love the high nutrients once they're big enough to handle

Did you recently increase light intensity? If not, this doesn'tlook like light-related. You have developing internodes (stem between growth nodes) and that means it's not getting stunted. Plus, the damage would be on the top leaves, not the bottom leaves - or at least progressed further than bottom leaves. Stretch, or lack of, guides light intensity... map it out, take some notes about timing and power. it'll be repeatable. Either the soil is poorly balanced or too hot or ph issues... more than one cause for this effect and not enough information. If you haven't fertilized yet, add that to the list... but that depends a lot on how hot the soil is. This looks like pro mix hp or bx, which would only have a very light charge that lasts a week or so.

Lost my answer as I closed the window.... had a lot of info types out but not going to redo it. In short if your light is the T24 by ac infinity from their whole tent growing package, a 18" hang height at 100% its a DLI of around 41. so a dim of 40% should be fine. Cannabis can take a lot of light from the get go. I think this is more about your medium and what you are feeding them. Look up the manual for your light and see what they say. the T24 recommended 18" at 30% so 10% more should not cause that big of a difference, assuming that is the lights model. Good Luck!

Personally I start my seedling under a spider farmer sf-2000 which is only a 200 watt light and I usually start the first week at 35% and I put little cups over them to help with humidity and light intensity during the first week ( until they’ve reached the height yours are currently at). May be a recoverable light stress too early on for those girls to need it. But my other question is what nutrients, I’ve had seedling look like this and eventually die due to too much and too little nutrients in my seedling cups. Nowadays I give them the regular soil mixture as I would for veg when using seedling cups