in my experience with mushrooms, they don't like pristine water. They also don't like high flow and must be acclimated to high light. As for growing, they won't grow right away, they need to be established for quite a long period of time, then they will suddenly take off when they are ready. I had red and blue mushrooms as well as a yuma that didn't multiply for almost a year, but then all of the sudden over a few short months they were everywhere.
If you are referring to growing size wise, try feeding them with something like rod's food or marine snow or something like that. Research it tho, because I'm not sure which one benefits them most.