Coloration is usually achieved when N&P ratio is balanced and consistent. Most colorful reefs have many fish, well fed, and an aggressive nutrient export plan. The trend these days are for many, myself once included, to get locked into the numbers game, to the point of starving their corals. ULNS are great as long as you feed the fish, which in turn feed the corals. As a general note: Corals exhibiting darker tissue usually implies that the nutrients are relatively high with browning coral. Conversely: Corals that show pale/ bleached, or faded coloration, usually implies that the nutrients are too low, and the corals are in need of food source. I would likely lean toward the fact that your nutrients are probably a tad high, IME, corals will grow in a nutrient high environment, however, usually have a hard time with growth in a nutrient deficient environment. Hope this all make sense, perhaps run a test on PO4 and NO3. Best of luck...
