This is my first flock of chickens. We've had them since March and this is the first time I've had any kind of ailment with them. I have 6 but only one has one of her eyes almost shut. It's not swollen just almost closed all the way. Today was the second day it was like that. I gave her some ACV in the water but other than that I'm a complete newbie! What would it be and how do I treat it? Also do I need to worry about the other chickens getting it? Thanks!