I had a M cap I had under my center brace on my 90. I rearranged my tank and bleached it totally white under the brighter light (550 w VHO). I left it there because it was about 6" across grown from a tiny frag and i figured I could grow other stuff on it. A month later it began to color back up and started growing again but up instead of outward this time. I'd leave yours be for a while and see if part or all of it comes back.

-Erik