I have a 12 week old Spitz cockerel that as of this afternoon can not stand. When I gently pull his legs out, he pulls them back under him. He extends them out when I lift him, but he can not support himself. The other 2 in the coop with him are fine as of right now. His crop is full just like the others. Any ideas what is going on? I have sulmet on hand, should I give him that? I brought him inside.