I've seen that look before and it may be nothing at all. Check your ph to make sure it is where you want it and then relax and let her do her thing for a bit.
I wouldnt worry bout that i've had loads of seedlings leaves go like that. I dont know what makes it sometimes go like it dose but my plants turned out ok.
I have had plants that are soooooo extremely healthy and beautiful throw some weird leaves...normal.
Just keep an eye on it, my opinion is that it is nothing.