You would have seen that type of change 6 months ago. If male rabbits eat less after puberty, my male bun did not get that memo! My boy always wants “more”, and he eats a ton of hay.
It sounds to me like you should try giving your bunny a variety of hays and see what he likes. Hay can vary from season to season, and between “brands” as well as between cuts of hay. For example, many places offer a choice between 1st, 2nd, and 3rd cuttings of timothy hay, going from stalkier (high fiber) to all leaf (less fiber but still ok) — Oxbow doesn’t distinguish between cuttings so if you use Oxbow hay, some bags will be 1st cut and some 2nd cut, depending on the time of year or bag. You can test your bunny to see if he likes a softer hay or coarser hay, with 2nd cutting normally being a good compromise. Orchard hay is all leaf but still a great hay and is supposedly sweeter tasting to the bun (my lops love orchard hay) and is usually the alternative when the human is allergic to timothy. Oat hay, meadow hay, brome are also options. My lops get a mix of orchard and 2nd cut tim, and my other bunny has decided she will only eat 3rd cut tim right now.