james, I'm coming off a similar situation. I didn't have fish in my tank, just corals. Then one day poof, pods all died, candy cane, polyps and other corals stopped opening, even a mushroom, I immediately relocated everything, but lost one colony of my prettiest polyps, but a stray one of the same colony lived.
The candy cane died slowly. Everything else is slowly coming back.
I got into some bad water is the only thing different.
I am in the process of setting up my ro system today. no more chances.
I used tap water for quite awhile, then they purged the fire hydrants, and since a dieoff of macro and pods back then, I started using ro from vending machines. I know something changed in the water system as now the toilet seems to grow a black mold type scum at water line, which it never did before.
I had some water on the back porch in the sun and topped off my 20 with it (ran out of ro), and the next day, poof, major trouble.
One thing that may have happened is that the extra circulation kicked up some detrius and started a mini cycle. By the time you tested, everything else could have gone back to good condition, but leaving a wake of disaster.
I doubt it was the korallia. But lesson--always disinfect used equip.
