i had the same problem with my ornge ball sponge. but the problem was with me and a mistake when i was doing some cleaning in the tank it fell out from where i had it placed and i picked it up and pulled it out of the water to get it across the center brace of the tank by the time i relized i just pulled it otu of the water was to late... short time later i noticed it starting to bleach......
i remembered seeing this video of reefkprz on how to frag ornge ball sponge
(by the way thanks reefkprz) so first i cut off the bleached part and then fragged it a little more to make 2 pieces and completely get rid of the dead or bleached area. since then everything has been great with it appears to be happy and is growing