Why do you assume i didn't treat them? Not everyone is living in the us and has the same brands available, but i went through dips of peroxide, iodine and coral rx. Also full tank treatments of Cyano solution (antibiotika), DinoX and Reefhd Flux.
The problem is, of you are patient like me and don't start the treatment instantly the zoa colonies look slightly unhappy, they are done for.
Just look how many threads are dealing with zoa problems. The overall majority of them never recover.
OP had low nutrient issues which can start the zoa degeneration on its own or make them susceptible for other diseases. In the end we never know.
I assumed you didn’t treat them (or were unable) because you said ‘ Right now a bacterial infection is destroying several of my zoa colonies and there is nothing i can do.’
In reality it seems like you’ve tried a bunch of things. Totally understand the same products are not available everywhere.
I’m not patient when I start to see a zoa looking off. I have a large collection so I’m usually dipping a few things week to week. Immediate action has saved stuff time and again. I’ve got a pretty good track record of turning stuff around.
There are a lot of threads about treating maladies but not lots of great pics for documentation. Still, it’s important people 1) research and 2) ask questions. If even 1/3 recover that’s not bad.
I agree the phosphate is lower than desired. I’m not going to attribute all of OP’s issues to that. However, it is just part of keeping zoas that some strains will randomly melt.