I let my two sizzles out to play today. They are to small to go alone. The older chickens still peck at them. I noticed my little roo kept laying on his side when he sat to rest. So I picked him up. I noticed he has a bubble like air sack on his chest. I don't see any wounds. It's just squishy like a deflating balloon. Will this go away on its own. Is this dangerous. Will he die?