Two nights ago one of my hens slept on the coop floor rather than the roost. I did not expect her to survive the night, but when she did I tried to find the problem and I noticed her lower abdomen is very firm and her breastbone is protruding (meaning, not much meat on her). She is a small mixed breed that lays colored eggs. She did not get on the roost again last night, and although lethargic, she is in the chicken yard today and was sort of taking a dust bath (gently, not vigorously). I checked her vent and it seems a little dirty from loose stool but not swollen or infected. Any suggestions?