One of my hens seems to have diarrhea. The feathers on her back end are ragged and have poop on them and there is some runny poop in the run. This has been going on for a couple of weeks. None of the others have any of the same symptoms (I have 5 altogether, golden comets, 2 years old), though they have all been laying poorly all summer. We don't really have a vet close by that treats chickens. What do folks suggest?