There are a variety of things you can do.
1. Oil in the ear. I have successfully used oil in the ear for rabbits to get rid of mites. I've used it every other day for two weeks and bang.. no mites.
2. Ivermectin.. NOT for pregnant or nursing animals so exercise caution here. Also be careful on dosage amounts and DO NOT give to rabbits who will be used for food for at least six months. Paste ingestible or cattle type injectable.
3. Diatomaceous earth.. FOOD GRADE. Sprinkle on animal regularly.
4. Here is one person's method of curing it. NOTE: tea tree oil is TOXIC to rabbits so you need to make sure they don't ingest it.
6. Try using VetRX brand Rabbit Remedy. Some folks swear by it.