Typically pellet limitation is based on their current weight (or what their ideal weight should be). I think generally people range from 1/8c to 1/4c. I think the rule on Oxbow packaging is 1/4c per 2lbs on your rabbit; however, I know some people do it lower than that (i.e. a 4lb rabbit doesn't get 1/2c of pellets). The idea behind pellets is to help balance your rabbit's diet, if there isn't enough variety without them (so variety of vegetables + hay).
Maybe reduce back to 1/4c to start and see how they do. Monitor their weight to ensure they are staying within healthy fluctuations. What will be good is hopefully they will eat even more hay, with the pellet reductions.
Good on you for transitioning your rabbits to a much better diet! Their teeth, tummies, and bodies are probably very happy.