About 4-5 days ago I noticed my EE hen limping. It has gotten progressively worse since then and she is not having trouble even hobbling. Today when I went to feed them she stayed under the coup and I noticed one of her eyes was shut. I did not notice any puss or swelling. Any ideas? She gets layer, scratch as a treat, and free choice oyster shells and grit. Thanks for any help! ETA: she is about nine months old.