In my old tank, and in my frag tank, they grow like weeds. They seem to love LEDs, bright light and lots of flow. The colours also change a lot depending on light levels. I have some that have green flesh in high light, and deep blue when in lower light. I have been torn on whether to include them in my new build, because they have spread so fast in the past, and SPS frags were no match for them.
To the OP, move that baby more into the light and give it some flow and it should flourish. They also like a fair bit of nutrients.