can't see anything from the pic except possible white tips, You could try dipping it, need to know what your parameters are, that info really is needed for any help or advice to be given. what lights do you have are all other corals ok? a coral rx and iodine dip is the best place to start could be bacterial infection fragging may be needed and it would be stn rtn will turn the coral completely white in about 12 hours or faster.