Rex Otters Mounting? Growling?

Question
Dear Dave,

I have had 3 Rex Otters - brother, sister and daughter - for 8 months now. They were given to me by a friend who was moving away, and hadn't ever been held properly or let out to exercise. They have a new hutch now, but it's still not quite big enough and I might need to upsize again to relieve some of the stress that is taking place.
The male is neutered - this took place with their last owners, although surely they'd be pregnant by now if it wasn't a success?
He has recently succumbed to an urge to violently mount both of the girls in turn, without a trigger or obvious reason. He pins the girls down to the ground and is really quite cruel, in my opinion. I thought that by being castrated the hormones that desired this impulse would be stimulated?
However, the girls have started growling and fighting with each other, not viciously in any way, but swatting at each other or getting right down and glaring at each other in an aggressive stance.
They also growl if another rabbit approaches their run, which they never used to do before. They rarely run back into the hutch, but remain there and make this whiney, husky noise in the back of their throats. They are by far the biggest, oldest and most aggressive rabbits I have out of 8.

Are they growling in worry, pain, fear, aggression?
Also, why does the male still want to mount the females when he is neutered?
Should I put the male in a separate hutch a) next to theirs or b) far away? Then introduce him later? How would I do this?
Are the girls coming into season - is that why they're growling?

Of course, this is our first Spring with them, and we have lost contact with the previous owners. The brother and sister are 2 1/2 years old, while the daughter is 1 1/2. The girls haven't been spayed, but they should be getting jabs and we'll ask the vet about it then.

Thank you very much for your time,
Becky.

Answer
hi becky take the buck away from the does -they growl to show they are dominant and anything going into there cage will get a bashing -its just normal rabbit behavoiur.
when they fight they are trying to prove which is  the dominant one and one needs to back down.
dave.