I have a hen that has been weak for a while and she seems to be getting worse. Her other symptoms are diarrhea, her comb is pale and laying down on her head, her tail is not up and perky, and she has stopped laying. She is still eating and drinking. I have looked at MULTIPLE chicken disease sights and I can not figure out what it is. We bought her from someone and have no clue what the age is. We have other chickens and it did not spread to them. We removed her from the coop into another coop with one other chicken for several weeks now and she has not showed signs of sickness either. Any help would be greatly appreciated.