A freshly published piece is hypothesizing that SCTLD might actually be viral, not bacterial, because even with antibiotics, tissue recession and lesions can still appear. Not super helpful to your current charlie foxtrot of a situation, but worst case, this might be a situation where a long fallow period and rebuild could be a option short of going nuclear with bleach and rebuild. https://www.frontiersin.org/articles/10.3389/fmars.2021.750658/full