Help- Trying to Save my Setosa. Need Advice

I have a montipora setosa that has been growing beautifully in my tank.  Then a bloody mushroom decided to take a hike in my tank and attack my setosa.  I immediately moved the setosa to another spot.  At first I only thought the base of the setosa was bleached, but the bleaching is spreading up the trunk of the coral and now only the small branches look fine.  Will this completely spread over the whole coral or will it stop at a certain spot.  Should I cut the tips of the branches and re-glue in an attempt to save a bit of this coral or will the bleaching stop now that it is away from the mushroom and dead spots really won't spread.  Anyone ever had this problem before?  It was such a nice coral piece, it was really starting to branch out and spread and I would hate to lose it.  Any suggestions?