Lighting

looks like a little tip burn... seedlings can power their own growht for 10-14 days. If this is a hot soil or you fertilized ... likely the cause of it. I'd wager the soild is a tad hot. i wouldn't overreact to it unless the plant falls over... it'll quickly become more robust and handle it. if oyu did fertilize, stick to water only next time and maybe get a little extra runoff to help leech out some nutes. stick to regular irrigation practices.. allow top to dry a bit before irrigating.. in a large pot you let top 1" dry, but in little seedling trays i'd do it a bit earlier obviously, but still wait for top to dry a bit. Always fully saturate subsrate. Dry pockets are bad news. a little runoff ensures that... you may not need as much runoff as a soilless grower would, but do get some to ensure you got entire volume wet. rinse and repeat when 1" dries up top.

Looking at your diary I see no lights listed so I can't tell you if you should raise it or not.. but I noticed you also don't have the pH of your water listed either. My guess is the water your using is not all too healthy for your seedlings and should pick up a pH tester and a tds meter

Yes it does look like light stress. One way to tell when your lights are to close is the leaves will start pointing up and you can also get twisted growth. I would back the lights off a bit and see how they do The white wont go away so watch the new growth. If they start to stretch then you want to lower them. Also since your container is clear you might want to fill the other empty spaces or cover them. Roots don't like light. Happy Growing