What kind of situation did they come from? I had the very same thing happen when I took two hens and a rooster. Rooster was crazy sick and the hens were just fine. Turned out they had been living in a very wet environment and the crowing rooster was sucking all of that stuff in with every cock-a-doodle-do! while the hens, who were not laying age, were not. They also had a nasty case of mites we treated with elector PSP. I luckily had a vet, who suggested keeping them in an open-air environment and a simple anti-inflammatory. It was a rough go for a long time, but he snapped out of it just fine. The vet thought it was fungal, so no antibiotics would have helped him anyway.