I have 5 backyard layers. 1 of them has been lethargic for 4 days now. green poo. comb and beard are droopy. I will not put a lot of money into her at vet. they do have an antibiotic to add to water at farm supply store. should I buy that and quarantine her. I don't want her to suffer either. will this illness pass or will she? the other 4 birds are fine. I checked vent yesterday, there doesn't appear to be an obstruction.