Merry is a dutch bantam roo, and he's something like three months old. A few weeks ago I noticed he was slow and sleepy. He eats, except he does these weird convulsions with his neck that I sometimes see the other chickens do to get food down. Also, he sometimes "vomits". When he puts his head down, a clear yellow goop falls from his mouth in a trail. I kept him in a crate for a couple days, but he wanted to get out. I let him out for some exercise, and he wandered all over the place, so I thought he was fine and I put him back with the others. A few weeks went by and there wasn't much difference. He doesn't seem to growing (his comb is still quite small while his brother Pippin's is enormous and he's already crowing). I checked him and he's extremely skinny. Now he's in his crate and he's eating a mixture of chicken feed (wet) with butter (to maybe fatten him up). It saddens me to see Merry so skinny and pathetic next to his healthy brother Pippin. Any ideas?