She might have had a prolapsed vent, but the reason she is bloody is that the others have pecked and damaged her vent. This can lead to cannibalism. A prolapse is a common cause. But I would examine your others and watch their behavior toward each other. There could be a bully. For now, she needs to be separated in a dog crate with food and water on a clean towel or puppy pads. Clean her vent with saline spray or a wound spray. Keep the red area moist with honey, sugar, or mild oil such as vaseline, hydrocortisone cream, or coconut oil. She might benefit once a day from a warm soak in water. Salt 2 tsp per gallon can be added to the water to make saline. Make sure to tell us if she is pooping. Tomorrow it might be easier to tell if she has a prolapse.
