Since he’s under a year old he should still be getting alfalfa pellets regularly, but he doesn’t need unlimited like he did as a baby.
And yes you can start introducing veggies, although if it’s easier to wait till his bonded mate is old enough you could wait another month (usually veggies can be introduced at 12 weeks). You want to start with a small amount of one veg, and then slowly increase it a bit over a week. If that goes well, you can add in another veggie. Romaine lettuce is a good one to start with, it’s well tolerated by most buns.
FYI and unrelated, keep a close eye on them in case some issues pop up when her hormones kick in. If you plan to get her spayed as early as possible you are less likely to have issues (4 months is the earliest that an experienced vet will do it).
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.