They're definitely slow growers. I've spot fed one of mine and it did grow faster, but I'm just too lazy
My other one was a bit of a rescue coral with only 2 polyps when I got it. When I spot fed it one polyp died, I'm not sure why, but now I a little reluctant to feed it again. Now that it's up to 6 or 7 polyps I think I'll try feeding one polyp and see what happens.