I have 13 hens and one rooster, one of the hens just died today. Yesterday she seemed to be fine. This morning we found her just lying in a nest. She had diarrhea and was very lethargic. Her crop seemed soft. This afternoon she died. We added the full grown rooster two weeks ago who had come from a friends healthy flock. We kept him seperated for a week and then he kept getting out of the temporary pen and in with the girls so we let him stay. She was about 18 months old. I don't know if she was laying recently or not. I'm sad for her but worried that the others may get something and die. Any ideas what this would be?