Clownfish not eating

Hey, I have 2 Ocellaris and one of them never seems to be eating at all (at least not that I see) I got my first about a week ago and the first day or two he ate but only a little and what was right in front of him. (now he moves around more though). My 2nd clown I got 2 days ago and he's a tiny bit bigger, Since I got him he has some filmy looking stuff on him and doesn't look as good as the other one. I hope he's not sick, and he doesn't seem to be eating much either. I have tried feeding him mysis shrimp and marnie flakes(which my other clown seems to love). BTW these 2 clowns came from the same place, and the 2nd one is a little bigger. Any idea why he's not eating? Also this morning I found him at the bottom of the tank, which the clowns are never there. But after turning the lights back on he seems back to normal, just not really eating.!?!??!?!?!?!

Thanks,
AC

no, not a maited pair but they seem to get along well, and the bigger one is the one not eating, the water is pretty good but nitrates are probably a little high, which might be causing stress.