I have a 6 month old Cochin Rooster that was running around and chasing hens three weeks ago. But since then he looks like he is on stilts and doesn't want to stand for very long. When he does get up walk, he is very stiff looking. I checked out his feet and there doesn't appear to be anything wrong with his feet. He never crows anymore and does like to eat (sitting down at the feeder). He has good weight too. Any idea what might be wrong with him?