cornish x have diahrea

[giantdvl]

I have 6 Cornish X's that seem to either have poop stuck to their butts or diahrea and the feathers under their butts are gone. Don't know what to do for them and how to treat them. Any suggestions. Also any suggestions on the feed they are eating? I'm feeding them chick starter right now. They are two and a half weeks old.

New to this site so be gentle. LOL