Open Brain faded ~help!~

[ScubaGirl]

We have a beautiful little purple, red and green open brain coral. Recently it has started to fade to a more flesh toned color where the purple and red were. The green is still vibrant though. It looks like it's going to start dividing too. It feeds well. I've even done direct feeding about 30 minutes after turning out the tank lights and it takes it easily (mysis and blood worms), just to be sure it's getting food.

Water parameters are all great. No nitrates showing. I even took my water in to the LFS to confirm it. We are changing the water about 20% every 4 weeks.

I tried Googling it too and didn't find much that I'm not already doing.

Does anyone have any suggestions? I would really appreciate your help. I really want to save this coral if I can.

Thank you!