One of my hens started having a dirty behind lately so I cleaned her up and treated her for mites, lice and wormed her and the rest of my flock to try and solve the issue thinking usually that will fix it however this did not work. She was still acting very normal apart from having a messy behind until yesterday when she was moving a lot slower than normal. I have given her another bum bath and have found a rather large swelling just under her vent. It is very squishy and doesn’t seem to bother her when I touch it. I also don’t think she is egg bound. I have felt around and can’t seem to feel an egg at all. I don’t know how old she is as I bought her at an action a couple years ago so I know it could be age related but I’m just curious. I have never had this on any of my chickens before. What do you think it is? Her comb nice and red and she is still interested in food but just looks very sleepy and is moving quite slow.