Chicken Sick - Help!

[Chickens4Lillys]

Black Sex-Link is sitting in corner of coop, not eating, barely drinking, listless and has one eye matted shut. Area around that eye seems excoriated/raw. She is also mouth-breathing. We just got her and three others three days ago. Others seem okay so far. We are just starting out with chickens...would antibiotics help? If so, which one? Help!

 

[Noobchick]

Have the others been picking on her? How old is she and the others?

 

[Chickens4Lillys]

The other night, one of the others pecked at her when she was attempting to eat with the others. Yesterday I went back and observed, and she is eating some and moving about; the eye is still closed; I didn't notice any others picking on her yesterday when I observed. ?????