A few days ago, we noticed that our Wheaten Ameraucana rooster was not looking like his usual plucky self--his tail looked scruffy, we thought he might be sneezing a bit. Otherwise, he was eating and acting pretty normal, but not crowing much so I thought he was starting to moult. Today, I noticed that one of his eyes looked really weird--like the iris has gone almost completely black. When we picked him up it sounded like he was breathing hard. We isolated him from the rest of the flock in a big dog crate that we use as a hospital crate. He is eating and vocalizing a bit, but nothing like his usual crowing. Does anybody have any idea what might be wrong with his eye? I have searched online a bit and I am stumped.
The photo below shows both eyes. We are really worried about him. He is the most docile rooster I have ever met, and he comes from good stock.

The photo below shows both eyes. We are really worried about him. He is the most docile rooster I have ever met, and he comes from good stock.