We have a hen who is at least four years old, probably older. Just this year, she has lost a lot of muscle in her legs and seems very uncomfortable on the perch. She sits down a lot more outside, just to rest. She is very top-heavy. She has a lot of fat on her around her crop and other areas. She is not underweight; I check her keel a lot just to make sure that she is keeping muscle on there. She had a weird egg a few days ago, but I haven't seen anything like it from her before and she hasn't had one like it since. She seems to be in good health otherwise, but I'm really worried about her legs. None of our other chickens are like this; we got her when she was already grown. She has always had a large crop and this body type (though not to this degree); though it has never caused her problems. Can anyone help? Thanks!