Our rooster, Red, was fine last night, but we got up this morning, and he can't walk. He's breathing hard, and has very smelly green stool. This just came on suddenly with no warning. Nothing has changed in the coop or chicken house, no new chickens or different feed or anything. Our chickens have always been very healthy. We took him out of the coop and put him in a cage in the shed, but I'm very worried about him. Any ideas?