I picked up a frag about a year ago. Put it in the middle of the tank under 2 120watt LED's. It has grown to about 10" tall and branched out to about 6" in circumference. (Mutiple brances) While cleaning one day, I broke off a piece about 6" in length. I move and mounted that piece to the other side of the tank. Within a day it turned brown. But after about a month, the color had come back.
I think I agree with the post about them not liking to be moved. I have had LED's for a little over a year. ALL of my corals have had fantastic growth. Better than when I had halides. So, I am positive that the LED's are not the problem. (Just remember that LED's focus the light better than Halides. So you should bring up the power percentage on LED's gradually, over weeks.)