My hens are 5 yrs old and one started acting lethargic about a 2 weeks ago. She was eating and drinking but moving slowly and all buffed up. About two days later she started diarrhea and her crop wasn’t emptying. I treated her for sour crop and she seemed to perk up a bit but 2 days later she was even worse and this morning I found her dead. I looked her over when I found her and she was just bones with diarrhea on her feathers. She lost an alarming amount of weight in a short amount of time even though I saw her eating normally. Any ideas wha might have caused this? I separated her from the rest of the flick at the first signed of illness. The rest of the flock is healthy.