Hello, This hen (6-7 years old) has been lethargic for several days. The first day she remained inside the coop, all fluffed up, looking ill. She seemed to improve slightly after a day, but she still spends most of the day just sitting on the ground; not even hopping up to the interior of the coop overnight during a cold snap. She drinks, and eats dried meal worms, and gets up and walks normally to get them. (I have not seen her eat the pellet feed, but I have not been watching her consistently so she may be eating it.) This morning I noticed her beak seemed to have a whitish - yellowish crustiness to it. We have two other hens who seem perfectly fine. In the top photo her beak is wet; she had just had a drink. Middle photo is clearer. Bottom photo was taken last summer, for reference. (A face only a mother could love, but her plumage is gorgeous!) Any thoughts? Many thanks!