Goniopora are very difficult to keep, I’ve had one form a spot like that. It spread a little and a few polyps died. No changes in tank whatsoever. Eventually new growth overtook that spot and that was the end of it. I love these corals, my pink Goni is stunning but constantly challenges me and I would classify it as temperamental at best. Based on that though and my experience if you start changing things trying to bring it around it is easy to do more harm than good. I’ve learned to just let it do it’s thing, maybe not best advice but this is just my experience.