I have two chickens that are acting very legarthic and with their neck feathers sticking out. Crop is empty. They are buff orpingtons less than 1 yr old. They are free range but have been inside for two days since the cold weather set in. One of the orpingtron hens has the same symptoms to a lesser degree. This is a mixed flock so the orps are to some extent "picked" on.The rest seem to be just fine. Please someone tell me whats wrong??