Evening,
Sorry you are going thru this.
@Rmckoy said the best bet for survival. It is not BJD. I have had this happen, as many of us have. I have researched for a long time trying to find a cause and a cure. Never found a cause.
The only way I can say to stop it is by fragging. Branching type are easy. As others mentioned once a head starts, snip it at the base it it will usually stop. I have left branches thinking it would stop on its own before. After losing 4 I would ship them and it was over.
I never did wall, but I would checking into if you are able to frag. If you can get all the skeleton out and leave only healthy skeleton fully covered in polyps is should stop.
This is based my experience after going thru everything I could think of