I would recommend cutting out the alfalfa hay completely. Manna Pro Family Ration is an alfalfa based pellet, so your rabbits are already getting a fair amount of calcium from that every day. Adult rabbits are recommended to have timothy hay in unlimited amounts and a timothy based pellets because of the issues with excess calcium that were mentioned earlier. Sludge and stones are not fun to deal with in rabbits and can be very expensive. The Manna feeds were developed for show breeders who typically use and discard their rabbits within 2-4 years -- these rabbits are breeding (requiring the extra calcium) and are discarded at such a young age that they don't see/experience these long term health issues.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry