As a first time rabbit owner, I highly recommend you go through the sections of the RABBIT INFO portion of this website to get the basics and a great overview of what you need to know and expect.

Since they are getting alfalfa hay, and if they are eating a good amount, you may be OK with just getting the young-adult Oxbow pellets, if that’s all you can find. The first ingredient in the adult pellets is timothy hay instead of alfalfa. A little calcium in the pee is all right, as rabbits naturally secrete excess calcium in the urine. If you see the pee is consistently white/cloudy/chalky/leaves a white residue, then there’s too much calcium and backing down is best.

The best diet, based on what you have now is continuing with plenty of alfalfa hay and getting either the young or adult oxbow pellets. The “recommended” transition period to no-alfalfa (i.e. no alfalfa hay or alfalfa pellets; switch to timothy pellets and a different hay, like timothy or orchard) is 6 months; however, many people transition earlier because they notice lots of calcium excreted. Alfalfa is dense in the needed resources to help a growing rabbit mature, which is why it’s the focus of their young diet, but it is inappropriate once they are older.

Also, I want to note that while your rabbits appear to get along currently, they have reached an age where they may become hormonal at any time, meaning the relationship may change overnight (in some cases). A pair of rabbits once cuddly and lovable may become very tense and potentially dangerous as one or both rabbits acts in a manner to either mate, assert dominance, or be territorial. Rabbits do not really acknowledge family units, so brothers and sisters will both fight and mate with each other, regardless of whether they were separated at birth or not. Also, if they are the opposite sex, pregnancy is very possible (and I will add that rabbits are often mis-sexed, so even if you were told they were FF or MM at 8 weeks old, they may actually be opposite). Please note the discussion of intentional breeding is prohibited on this forum. My recommendation would be to separate them to prevent potential pregnancy and also ensure they do not have any disputes when you are not supervising. The safest recommendation is to separate them until they are both spayed/neutered, in which case you can then begin the process of formally bonding them (see the Bonding Info in the RABBIT INFO section of the website). With them getting along well as younger rabbits, it can make the bonding process smoother (in some cases), but not always. What can hamper a future bond is if they have grudges or bad experiences with each other, like fights as a result of hormones.

I would like to add that ideally you should use what you were originally using and mix in the new pellets. I have recently taken my guys to vet and two different vets still recommend even at a young age to rationing the pellets and alfalfa hay. They both want them to develop good hay eating habits even at a young age. I have heard good things about the Sherwood brand, Oxbow, and I am currently using the Supreme science selective brand.

the rabbithouse website has a nice breakdown of a number of different pellets (adult and youth).

Good luck

Ditto what others have said, sounds like you are getting on the right track!

Some people find it is easier to transition rabbits from alfalfa pellets to timothy pellets, vs. from alfalfa hay to timothy hay. So what you might want to do (slowly and gradually), is to transition them to a young rabbit pellet with alfalfa (oxbow is a fine one), and then transition to timothy hay instead of alfalfa. Then when they reach 6 months you will prob have an easier time removing the alfalfa because they will have good hay eating habits. 🙂

You could start mixing in timothy hay with their alfalfa hay now and see how they like it.