Welcome here! Congrats on the new addition, and thank you for adopting rather than buying!
Everything I think I have seen has said unlimited pellets, which is sort of unclear. At 7 months, it is recommended that you reduce to 1/2 cup per day… and then gradually reduce further to 1/4 cup per five pounds of bunny. I’m sure you know this since you are an experienced bunny person.
How much are you feeding him in a day in real measurements? 1/2 cup, 3/4 cup, full cup? If you’re not scooping pellets with a measuring cup, I’d suggest you begin so you’ll have a good idea of what he is actually eating. When you feed him 3x a day, does he right away go and scarf them all up? Or does he eat gradually during the day? I guess you could keep some in his bowl all the time, just make sure the hay consumption is still good.
What pellets are you feeding? Babies can have alfalfa pellets up to 7 months, but if you are already feeding your other rabbit(s) timothy, you could stay with timothy and just give the baby some handfuls of alfalfa hay in addition to the timothy hay.