I don't know what's in your tank.. I don't really know. I just so wish there was a way to find out.
If the rest do okay then it must have been a transient thing - and like you say cannot be figured out.it is just going over information that has already been gone over, or looking for something that due to other factors cant exist. I do not know what caused it, I have binned all the corals that looked like they were struggling so as not to infect any corals I am selling in the shut down
As am I.Just an objective observation here - I think @aussieant32 is well over trying to figure this out.