Dirty Lilly Stream My Rabbits Behind Is Getting "dirty" Everyday?

My rabbits behind is getting "dirty" everyday? - dirty lilly stream

ok .. I know a lot about rabbits, but my rabbit, Lilly, is "dirty" every day
My parents told me what happened to one of the rabbits before and after cutting hair in the area ...
Is this a good idea?
If you have any other ideas plz say