I'd remove the ROX carbon. That's very aggressive stuff, especially for a tank with no fish in it. How do you have 10ppm nitrates with no fish? Is this a new tank?
Being that this may be a new tank and it is a 4 - 6 inch colony, I'm going to assume this is one of their maricultured pieces that was grown out in a shallow lagoon in the Fiji Islands. If so, these aren't exactly the easiest pieces to keep, especially in a new tank with no bioload. Many times these pieces will RTN or STN in a perfectly capable and established SPS tank that's thriving. They really are hit or miss. Looking at how far along it is, I wouldn't get my hopes up. I'd also start adding some small fish and feeding them, because your other corals may start getting pale as well.