Gosh big difference, usually when you have a chick that doesn't grow isn't eating good, lethargic they usually don't make it. You just have to do support and hope something helps. @casportpony thinks you should do corid I don't think it would hurt at this point and may help. She sure knows alot more about meds and treating than I do.
As for what to feed maybe try mixing some warm water into some of the chick starter making it like thickened soup and see if she goes for that, I'd just do a small amount first.