Help needed...

I have 2 lil bunnies approx 9-11 wks old, 2 females we think?? They are from the same litter and have got on great since we got them home, cuddle upto each other, groom each other and seem gr8 friends but over the last few days they have been chasing each other round and fighting?! Fur flying evrywer, no damage done tho. We have ended up spliting the hutch in two, we put them 2gether 2nite in the run and they we gr8 again, put them bk into the hutch 2gether and the run that is attached to the hutch and fighting again....really dont know what to do.... Ne ideas muchly appreciated :|