For columanaris which i don't think you have you do dose 2 meds at the same time a gram negative and a gram positive, furan 2 and another of a recommended as the are many different people prefer.
the key here is super clean water don't over do it and kill your BB, it looks like fungus but does not look like columanaris as I've had it and almost made me give up the hobby as it killed every fish but 2 which was 31 total (I was a beginner and didn't know about anything), CB is very knowledgeable about these types if things especially diseases and rams, I would honestly take his advice and bump the tank up slowly to 82 and that will also help white spot, but if it is columanaris it will make it spread faster from what I've read and been told.
Edit : just read your post about alot of fish dying which does indicate that it is columanaris which will kill your whole tank if you don't take action now I mean yesterday, furan 2/triple sulfa/myracin 2 etc etc CB would be better to recommend than I, but I will say this with confidence get garlic guard or make your own to soak the fish food in because if they won't eat they can't fight infections.
the key here is super clean water don't over do it and kill your BB, it looks like fungus but does not look like columanaris as I've had it and almost made me give up the hobby as it killed every fish but 2 which was 31 total (I was a beginner and didn't know about anything), CB is very knowledgeable about these types if things especially diseases and rams, I would honestly take his advice and bump the tank up slowly to 82 and that will also help white spot, but if it is columanaris it will make it spread faster from what I've read and been told.
Edit : just read your post about alot of fish dying which does indicate that it is columanaris which will kill your whole tank if you don't take action now I mean yesterday, furan 2/triple sulfa/myracin 2 etc etc CB would be better to recommend than I, but I will say this with confidence get garlic guard or make your own to soak the fish food in because if they won't eat they can't fight infections.