I've always noticed my hens will have poop stuck to their butt every now and again. I have 17 adult chickens and they all rotate with having and not having diarrhea on a regular basis. They get Purina Layena in the morning in three separate bowls, and are let out to free range around noon. They are laying fine, and have cool water 24/7 and shade. Otherwise healthy chickens, no one is sneezing or coughing, all 100% healthy otherwise. The youngest are six months old and were raised on Medicated Feed but are also now on Layena as they are laying, but have not noticed diarrhea on them yet. The oldest is a 7 year old Orpington. The worst ones are my purebreds, which are three Orpingtons and a Cochin Bantam. Wondering what would be causing the diarrhea and how to help it?