Girls behaving badly

We had our 2 sister rabbits neutered in Feb and they have settled down well since, except for the last few days one seems to be humping/nipping/chasing the other ... mimi ended up with cuts/scratches over her ears and there was fur from both of them in the garden. We never saw them fight or anything, so wasnt sure it was sydney.

Then the other day when i got home from work there was a lot of fur in their hutch and a few scratches on mimi's ears again and sydney had clumps of her fur ready to come out - mimi was keeping out of syds way.

Whats going on with them, is this likely to get worse and should we seperate them and for how long, they have lived together since they were born and are now about 15 mths old?

Quite possibly another case of ''spring fever'' they will be having small scraps but unless you find serious injury leve them to it they will sort it out and peace should return at some point