Bum problems with year old rescues

[JLS84780]

I just added three little mutt barnyard hens to the flock. Two of them have obvious issues and I could use some advice.

Black one has missing feathers on top of her tail. I was told she had an aggressive rooster on her and all were treated for mites in February. I'm not too concerned but if I should do more than just an improved diet please let me know.

The grey one is a true mystery chicken. She might have some game bird cross or is a variety I've never seen before. She's very timid/flighty and has the most crazed squawk when caught I've ever heard. Her vent is pretty red so I do think I need to do something for her but I don't know what. She's also very low to the ground and I'm not sure if that is normal for her or not.

They are all laying. The grey one might have this blue egg?

 

[FrostRanger]

Can you post better pictures of the one with the red bum? The first one I think is almost certainly rooster damage and there really isn't anything more you can do beyond what you're already doing. Her feathers will grow back during her next molt. The other one might be rooster damage too or feather picking but better pictures would be needed to rule out anything else that might be going on

In any case it's always a good idea to check for lice and mites anytime you're dealing with unusual feather loss just to be on the safe side. Overall I think you're doing a great job with them so far!