These are our first chickens. They are around 16 weeks old. Last night when I shut them up everybody seemed fine, but this morning Jay the Speckled Sussex was lying down on the floor of their coop. She can walk, but really slowly and wincingly, not with an obvious limp on either leg but clearly walking hurts her. She was following the flock around this morning, but she lies down again as soon as she gets where she was going. I looked her over and could not see any injury or any sign she was sick, but again I am new to chickens and could be missing something. She is eating and drinking, although I think not very much, but I set her in a wire cage under the flock's favorite tree with her own food and water. What else can I do? What should I be looking for? Please help, there are going to be tears around here if we can't get her better.