2 neutered males suddenly fighting. help please!

Any input would appreciated!
I have 2 boy Holland Lops, Oliver and Romeo. I had Oliver first and got him neutered, I added Romeo and they were incredibly bonded, best bunny friends, always grooming each other and cuddling. I kept Romeo UN-neutered for the past 10 months and it was never a problem. They got along great! I neutered Romeo 2 weeks ago and when he came home from the vet, Oliver was very happy to see him and everything was fine. 4 days ago they got into a fight and afterwards they seemed fine and were getting along. As of last night I can't have them around each other without them fighting. I have had them separated since last night and tried to put them together earlier this morning and they went at it. I'm really confused!! Can anyone help me? They were so tight and close and it seems things are worse now that Romeo is neutered. Has anyone had this happen?
Thanks.... =(

I would give them time for hormones to settle down and for Romeo to heal without stress. Sometimes when one goes to the vet and comes back it can confuse the other animal or change the dynamic. Try slowly introing them from the beginning again in a few weeks once they have time to forget their fighting I'd say. I've heard of bunnies falling out of a bond before but hopefully it wont be permanent for you.