HELP Coastal banksia in distress

My coastal banksia has been in a bit of trouble for some time. It started a couple of years ago when I built up a level of soil around the base of the trunk, which I now realised was a mistake. I removed the soil some time ago, but feels like the tree just getting worse, that pests/disease have really moved in. Lots of dead branches, distorted foliage, galls on seed pods, the whole thing v sickly looking. I suspect spider mites is one problem? There’s also loads of scale on a neighbours tree that’s very close. Any ideas? Any solutions? Thanks! 🙏