Hi, first time posting. We recently took one of our chickens, a Dominique, to the vet because we noticed what seemed to be blood dipping from her vent. She's one of our less tame ones so we hadn't been able to get up close and check it out. Turns out she had a sizable hole directly below her cloaca full of maggots. We and the vet assume she had some small wound and then flies laid eggs in it and the maggots enlarged it. It had dead tissue all around. Pretty gross. But we've been medicating her and she seems like she feels much better since the maggots have been cleaned out (I know I would). Today we started inspecting and cleaning our other six hens because we realized they have gotten lice. We noticed that one of our Silkies who has always had a particularly dirty vent ever since we got her, has a little "hole" below her cloaca. It's more like a big blackhead, really, because it's full of what looks like dirt. There are no maggots or anything that we can see (just lice). I've attached a photo. Can anyone tell me what this is? An ingrown feather? A blackhead? Something to be concerned about?