My chickens are 5 months old. Last week I noticed that one had a closed eye and thought maybe it was scratched somehow. I now have another chicken that has a lot of white mucus stuff covering the right eye and the left eye has mucus starting to form. What could it be? What action should I take? Also the second chicken has some raw spots on her comb and I saw another chicken pecking at her head area. When my flock was new(6 weeks old), several of the birds eyes closed and the person who sold me the chickens injected an antibiotic in the whole flock and replaced two chickens. Could this be related?