Its distinctly possible that the bulb is getting old. I think replacing it might be the first step. The corals I've bought have had great color when I get them, but just never seem as vibrant in my tank. The best example is actually the maxima clam that I just got. It was amazing in Jason's tank, and although appears happy in mine.....just doesn't "pop" the same way. I'd love to make my critters look as awesome as they do before I bring them home!
I think part of what I'm noticing is that the tanks that I idolize look more blue, whereas my tank appears more white. Some of this I'm sure is immaturity and a lack of grow in so there's less coral to look at. Thankfully my coralline is starting to really come in, but if there is something I can do from a lighting stand point....I'm in!