Kimbeensis help . . . turning green?

I just noticed around the lower section and the base of my Acropora Kimbeensis is turning green. I moved my light fixture towards the back of the tank about two months ago so it was directly above most of my SPS corals. The Kimbeensis was closer to the front of the tank and mainly received light on the top and back side of the coral. I picked the coral up today because I noticed the polyps on the bottom of the coral had not been extending for a few weeks and noticed there were no longer any polyps on the base or lower section of the coral. The lower section of the coral is all skeleton. Picture a beached (white coral) except instead of white the base is green. I moved the coral the be directly under my MH bulb hoping the color will come back. Can anyone give me advice on what I should do? Will the color come back? I hope it isn't a disease that will kill the whole coral because it is about a 2" frag. All of my other SPS corals are fine, my parameters are normal. The other thing different about this SPS coral is that there are a few Orange Zoanthids growing around the base and every so often I cut them off.

Here is a picture when I first moved the lighting fixture back. You can see from the picture that the base is almost completely dark because no light is reaching it.


Here is an older photo.


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i wolud keep a close eye on it and moniter bleaching, if it does start to bleach i have seen peple brake off the bleached part and the res will be fine.