Time and patience.
Making sure your calcium, Alkalinity, and Magnesium is in balance.
Leathers and LPSs are usually really fast growers. Before you know it, you'll be fragging them off for the Frag Fest 4!
I don't target-feed my frogspawn. It gets whatever it can catch that drifts close to it when I feed the fish. And fish poop. Well, maybe sometimes when I add micro-foods like Acan-Plus to feed my Acans, it gets some by default.
Don't stare at the tank, either, it won't makr things grow any faster!LOL.