I have a question about 1 of my Nankin hens, ever since it got cold she's really lethargic and she sleeps alot and stays puffed up. But when I feed, she perks right up. At night she can't get up on the roost bar. This didn't start happening til it got cold. Now I have to help her up on the roost bar so she doesn't freeze at night on the coop floor by herself. She acts like she's going yo try to get up there but all she does is a small little hop that gets her about 2 inches off the ground, she won't flap her wings or anything. Any ideas what could be wrong? There's no nasal discharge or coughing/sneezing so I don't think it's a cold are anything like that. This has been going on for about 2 weeks now.