One of my chickens "hoppy" is acting very unwell, she is just lying around in her nesting box by herself and hasn't come outside for several days now. I don't think she is broody, she has never been clucky in the 3 years I have had her, and she has not been laying eggs for almost 6 months now. I think she is quite old, but I don't know how old, both of my dear chickens are rescued from horrible circumstances, so I try my best to make sure they stay well and happy. Hoppy has always been a well chicken, and while she has had some trauma caused by the injuries to her legs inflicted by her previous owners, she has never actually been ill before. She is not showing any outward signs of trouble, her colour, vent and feathers are all normal, I don't see any evidence of mites, and she's breathing and vocalising normally. I don't see her drinking anything but she has water available and will get up and eat as long as I bring the food to her. The only thing I have noticed that I've never heard before is a growling sound, like when a person's stomach is rumbling commong from her occasionally when I pick her up. So I am really at a loss as to what is wrong with Hoppy. I would be most grateful for some advice here.