Hen found bloodied with swollen vent!!!

[Farmlife16]

I found my hen yesterday afternoon with a bloody backside. After cleaning her off, I noticed some yellowish discharge from her vent. I suspect that she has a reproductive issue (I've noticed that one of my hens stopped laying the past few days and now I think it is her) and somehow that caused other hens to start picking on her. I'm not sure if she was already bleeding a bit before she was picked on or not. There are no signs of bleeding now. She is separated with food in water, but does not seem interested in either. I tried giving her scrambled egg with some crushed calcium, but she was not interested. I'm not sure what else I can do. Advice appreciated!!

Also, picks of her vent are attached below.

 

[Tookie]

It sorta looks like flystrike to me.