Live rock colour variations within a reef tank

[newreefer_59]

Still a relative newbie at this having setup my 150 gallon tank about 11 months ago. Have recently seen a noticeable change in the tank as some of the live rock has turned a darkish/gray colour, while some is still purple, violet, green and various others with a dozen or more poly's popping up from time to time. Question, should I be concerned re: the darker colour on some of the rock as per pics attached? Have also had some black growths on a few of the rocks that may show up on the pics.

I have recently changed the white lights to 54w 10,000K T5 HO's and tests are in the mid-range. Anyway, any thoughts are appreciated.