Doesn't look like bleaching to me; it looks like tissue loss (STN/RTN) in picture 2 and 4, which is somewhat common in wild pieces. If it has stopped for now just keep an eye on it, but if it starts again you'd want to frag off those pieces. Frag them just below where the recession has stopped (make sure not to leave any dead parts, so frag off a little live tissue with it). You can also superglue around the dead/live tissue border, but usually you are better off fragging.
Some people may also say to dip, but I have never done so as fragging usually work for it. I'd think that in dipping you'd stress the coral more.