Infectious bronchitis is a virus, so not antibiotics will treat symptoms. MG can be treated with Tylosin, Denagard (tiamulin,) oxytetracycline, or Baytril.
What is your general location? Do you have access to a feed store where you can buy some balanced chick starter? It sounds like you may be dealing with a chronic respiratory disease (CRD, MG.) It might also be a bronchitis virus. Those are infectious to other chickens. I would rinse the eye with...