You may need to try a different type of hay then. If the hay you're feeding is second cut timothy(most common one fed to rabbits), then maybe try some orchard grass or oat hay. There's also third cut timothy that might be an option(though it can be too rich for some rabbits). If trying different varieties doesn't work, you could try hay pellets. Standlee has orchard or timothy ones, that can be bought online, or some local tractor supply stores will have them. They are a larger size pellet though, but my rabbits never had issues eating them. I had a new rabbit that wasn't used to eating hay and wouldn't touch it, so I ended up feeding him timothy hay pellets, and he ate them fine. Over time, he eventually started trying his loose hay, then started eating loose hay fine without any problems. But it was the hay pellets that helped get him to that point.
How are your rabbits fecal balls looking? Are they a decent size or pretty small? The problem with him not eating hay and having reduced food pellets, is that he may not have enough food going through his digestive tract, and this isn't a good thing with rabbits as it can result in GI stasis developing. So if he doesn't start eating a different variety of hay or hay pellets soon, then something else may need to be tried. Sherwood has a complete timothy rabbit food, that basically is the hay that a rabbit needs, included in the food pellet.. So that may be an option to try. Or it could be his mouth may still be bothering him and that's why he still won't eat hay. So the vet getting another look at his mouth may be necessary, or even xrays to see if there might be something else going on below the surface.
