It sounds like they are fighting. When rabbits get hormonal – normally around the 3-4 month mark, they will suddenly start fighting. This is why its generally advised to separate them while they’re still babies and seemingly getting along. Rabbits will have extremely vicious fights – while it seems like you’ve been lucky and only some fur pulling has occured, I would highly recommend separating them immediately before it gets more serious.
Rabbits need to go through a bonding process. Just being together from birth isn’t enough. Separate them, neuter them, then spend a couple of months prebonding and bonding them. If you check out the bonding section of the forum, and BUNNY INFO, you can find more information on the bonding process.
For now, separate.
(When bunnies moult, fur gets everywhere, but it doesn’t come out in large clumps that stay together like it does when they fight. Large clumps can only have been pulled out by another bunny).