I always heard that pearls/jade and n'joy were slower growing varieties of the original marble queen. I found that mine started to really take off after I pruned it back and stuck a couple of fertilizer sticks in the pot. I've also got a marble and I gotta say, it's been keeping up with it growth-wise lately haha
I pruned it back and propped the chops (they also took foreeeeeever tp root) and replanted them with momma so it's looking ok these days. I don't think it started to grow any faster after pruning but maybe I'll try some more fertilizer.