One of my hens is sick, but I can't figure out what's wrong with her. She is growing white feathers among her black ones, and her beak turned from black to yellow (that started about a month or more ago). That isn't the sickness, just an observation. She seems to be slowing down, too. I know she is getting old, but it happened so quickly. All of the sudden, she wasn't going to her normal sleeping place when I go to close them in for the night (my chickens sleep on top of the nest boxes, about four feet or so above the ground), but sleeping on the ground. I keep putting her back up with them. I'm worried that she might hurt herself flying down, because she seems to have trouble walking, but it's getting colder out, and I want her to be warm with the others. In the morning, when I let them out, she seems to be limping almost, but then eventually regains her footing and can walk normally, just acts mellower. I saw her peck a couple of the others, so I don't think she's gone to the bottom of the pecking order yet. This morning, she didn't come out, and when I went in to see, she was lying against their little door. I put her outside to eat, and she acted like she had a broken leg, but then was able to get up and walk around. These symptoms all started happening about four to five days ago, maybe less. I don't recall her acting peculiar before that. Another thing is that her weight seems to have decreased. The reason why I mentioned the food is because I just switched them to the new food, NatureWise, more than a month ago (after her feathers and beak turned, before she started acting funny), because I got a few coupons for free bags. They usually have pelleted feed from Houles or Purina, and never seemed to have an effect when I switched feeds before. That's really the only thing that has switched within the last few months, so I thought maybe that was affecting her. But, all of my other chickens, even my other 5 1/2-year-old hen, haven't seemed to change at all from it. Anyone know what is wrong, or what I can do to help? Thanks in advance.