In my opinion, the more diverse a diet the better. I feed forage, any weed, grass, leaves, twigs etc. I can find, so mine are used to pretty much everything and get no problems when a new plant enters their diet.
I have little clue about that artificial diet many seem to prefer for her pets - most veggies were created for the human digestive system, rich, little fiber, and Alfalfa is very rich in protein.
Timothy, or whatever single spieces hay may have it's advantages over mixed farm hay - like less waste since they don't pick raisines, and I guess any available kind of grass of the sweet grass family will provide what they need.
So, what you feed now is a quite rich diet, great for bringing rabbits to butcher weight fast, in my opinion anything grasslike, less rich in proteins and more fiber you introduce is an improvment. The stuff that makes young rabbits grow super fast imho isn't the most healthy, the more different stuff they get the better, and they need fibers.
Any grass hay is very good for their teeth, I would start to replace that alfalfa gradually. Hay based pellets are an addition, I use pellets just as treats, just about 1 tbsp per day, so it doesn't matter much what they made of.
Also great additions are twigs to gnaw on, like willow or apple.
Anyway, introduce new things gradually - over one or two weeks.