I have a black hen about 3 1/2 who does't appear to have laid in a while. For a week or more her rear end below her vent was bloated and pretty big. She doesn't have feathers under hear tail so it was pretty apparent and the skin is reddish...but like the skin on my other hens who are missing feathers. So she looked big and bloated and was pretty slow and didn't do much or move around much but otherwise was okay. Now her rear end is almost deflated looking and the skin isn't taught but wrinkly and she just feels smaller and super skinny. Thoughts? Is it cocccidiosis? internal parasites? My other 10 birds don't seem bad off, what should i look for or treat? Thanks!