I have a buckeye chicken approximately 5 weeks of age, in with 17 other chicks of the same age and 8 guinea fowl in a well ventilated coop with shavings for bedding, just on grass as of yesterday. These were from a breeder flock and there have never been chickens on the property prior. I noticed a few days ago this chickens eye (the actual eyeball, not the surrounding tissue or lids) appears a bit swollen and when you look at it from any angle but directly straight it looks red, and the eye is partially closed, but she is still blinking and is shaking her head a bit, but otherwise acting normally. No discharge or other symptoms. Impossible to say what the stool looks like... All the other chickens have clear eyes and are acting normally. They were not vaccinated by the breeder against mareks. The other eye is fine. Any ideas?