Make sure it is stable...not "wobbling" in flow. Also, they like strong yet in-direct flow, along with lower nutrient levels as mention before. It looks like it is high up in your tank, which is good. I had a nice pokerstar frag brown out on me from stress of transporting it etc....I made the mistake of expecting quick color change and after a week in one spot I'd move it and so on. Finally I picked out a spot with strong light and strong indirect flow and epoxied it onto the rock.
Now, a month later, it is bright blue base with neon green polyps. New growth is orange poylps which turn green after a bit.
Good luck!