Bonded bunnies now fighting

Question
Within the past week (which included spending 3 days with friends and a long car trip), my two rabbits have started fighting.  Originally my 18 month old Bailey bonded well with 6 month old Bandit (both females)4 months ago to include grooming, napping, resting, and play-chasing.  Bailey mounted Bandit from the beginning, and Bandit didn't seem to mind.  Sometimes now Bandit puts up with the mounting, but other times escapes Bailey and a chase ensues with a little fur flying, both inside the cage and outside the cage.  Are the bunnies just off their schedule, is Bandit maturing and not wanting to be bottom bunny, or is it the change of season?  And do I let them "have at it" or should I intervene, or even get separate cages and allow them to play at different times?  Neither bunny is spayed (in accordance with my vet's recommendations).  Any advice would be welcome!!

Answer
While it is possible that Bandit may have decided she doesn't want to be the bottom bunny anymore, the best bet is stress and change in routine from the trip.

You may want to go back to bunny bonding 101 and give them a little bit of private space for awhile.  When you let them out together, try to find a neutral place like a room they haven't been in or a bathtub.  Have a squirt bottle handy or something that will allow you to separate them without getting bit.  If they start fighting, you want to break it up and put them back in their private spaces.  You can also try to put some food out when they're in the neutral space to see if they'll concentrate on food instead of their temporary friendship issues.

I'm curious why your vet recommends not spaying your rabbits.  Spayed rabbits are easier to maintain bondings and have less health problems.  If you plan to breed one at some point, it makes sense.  But a rabbit that is not spayed has a lot more territorial issues than a spayed rabbit.

This site provides some methods and tips for bonding rabbits that you can try to get your gals back together:
http://www.rabbitnetwork.org/articles/bond.shtml

Good Luck