This is my first adventure with chickens. I have 2 black australorps and 2 silver-laced wyandettes about 22 weeks old. None of them are laying yet. The wyandettes are hens, one of the australorps is a hen and the other is a rooster who was supposed to be a hen. They wander around the back yard all day and are secured in their run (16x8) at night. On Sunday the australorp hen, Cinderella (named by my daughter), kept hiding in the storage shed. I assumed she was getting ready to lay, so I put together a temporary nesting box for her as I am still working on the permanent box. I decided to confine her to the run since I've read that it is very difficult to retrain a hen who gets used to laying eggs outside the nesting box. She is suddenly very docile. They are friendly chickens, but they aren't lap pets. Cinderella now lets anyone walk up to her and carry her around. Monday I decided to check her over just to make sure there weren't any issues. Here is where it gets disgusting: her vent is stretched open. I can see a yellowish layer inside, some of it dried out. There is dried blood around the outside. On closer examination it appears that her vent is ripped open. She doesn't seem to be in any pain, but she must be. I put her in a separate cage to watch her appetite and to keep the other chickens away from her as I've read about cannibalism. She seems to be eating and drinking just fine. She does not have diarrhea. In fact, her poop looks normal. I can't find anything online that matches any of this. She doesn't look like she's lost weight. She hasn't lost any feathers and they look shiny and healthy. None of the other chickens have any issues. I've asked friends with chickens and they are all baffled as well. My only thought is that she laid an egg in the shed and the other chickens started pecking at the cloaca (which I've heard can happen). She's right at the age to start laying. Right now I'm letting her have the run to herself during the day and I put her in a cage in the house at night. I'm going to soak her bottom in warm water to loosen the dried blood and then apply some antibiotic ointment to it. Does anyone know what's going on? I appreciate any help.