The Zooxanthelle in those areas on the branches have vacated. The base is different however as it has the purple pigment but also still contains the zooxanthelle. So what you appear to be seeing is localised bleaching. I have this on a few of my frags after dipping so it appears stress related.
I have these two that are clearly having issues. One is a forest fire Digi and the other is a green milli.
Now you'll notice on the digi there are two branches headed up and one is cut in half. That is completely new as of while I was at work. This has to be the butterfly or the crab.