During the night we heard a commotion in the hen house and discovered 5 of our hens and our cockerel on the ground. Everyone was apparently terrified, but after examining the area we found no external injuries nor any predator. One of the hens on the ground however was wheezing and was beginning to breathe out of her mouth. It was obvious she was struggling to breathe. There is no external sign of injury. It seems to be isolated to her airway. She has not been ill so this isn't a pre existing problem. We don't have a vet who will treat chickens and I'm at a loss! Any ideas?