Initially my yellow polyps just set there barely opened. I tried various locations for light levels and flow, but for the most part they simply existed, and were nothing to brag about. My water parameters were fine........and everything else did super. Then all of a sudden (about 3 months down the road) those yellow polyps just up and started to grow and take on the typical look of yellow polyps, and opened up really great.......in about 2 months time they have more than doubled in size since they finally took ahold. So initially they were very slow, but now grow like weeds.
Same for my green star polyps. It has always looked fine, but after 1 month or so it really started to grow super fast..........now I can actually trim it or it gets to be too much and cover everything. No food necessary for either of those critters jut keep parameters of water right and they will do just fine.