Problems with my red open brain coral

[molybdenumman]

Best of the season to all.

I got an open brain coral about a month ago for my 55g tank. Colour was great until about a week ago. The red seems to be disappearing. Water parameters appear to be ok, so as the tree said to the lumberjack, I'm stumped.

The coral is on the sand bed partially sheltered by a live rock overhang. I have 2x55W 10000K compact fluorescent bulbs going for about 8 hours/day along with actinic lighting. There is good flow.

Is this colour loss common? How do I bring back that vibrant red colour?

Any help would be appreciated.