Just now following up, sorry.
A more defined close up picture (macro shot possibly?) would help out a lot. By the original picture posted it appears that some of the "bleached" portion appears to actually be getting a decent degree of light, otherwise it looks like a healthy colony. I have a SSC colony with MUCH tighter branching, probably due to very very high flow, that has little to no coloration on lower and side portions that receive very little light exposure. What you are experiencing might be completely normal, but it's very hard to tell without a more detailed picture.