Hi guys, I am new to BYC and to having chickens, I have 5 week old, Cornish Crosses. Over a week ago I noticed that one of my birds isn't walking right, he was off balance and would sit with his legs in the air in front of him, well a few days later he was fine. Then it started again now he is unable to walk at all. He does not seem sick, eyes are clear, eats and drinks well, but he can't walk. I have included a pic. (the purple on his wings is just Gentian violet, the other chickens was picking on him) Does anyone have an idea what could be wrong with him?