If burning is occurring, it will be subtle at first, browning on edges and maybe some spots. Whereas you are dealing with mostly cotyledon at this point, burning would be trouble.
Want to see dark green at the center of the first node.
seedlings look great! I like to keep a little wind on them with a fan - not too strong, just enough to make them shiver & sway in the breeze. It will strengthen the stems.
They aren’t as “clear” as I would like but, I am seeing roots. 2 Days ago I wasn’t sure if they were roots or bent plastic from drilling. Today they are roots for sure. I wouldn’t say root bound but the way they are growing In could happen in hours I swear.