Just reading through your description and I have been having similar/same issue over past year. Mainly acros they are growing well, happy and suddenly part of it goes white or all dies.
Anyways I suspect it is something to do with this:
I am not doing moonshiners , but have large collection of trace element bottles and the problem started when I tried to get these perfect parameters. They were perfect and detectable by ICP but I keept loosing corals.
I suspect the combination of dosing traces to detectable levels and adding fish and coral foods that also contain trace elements may push some over and leads to this unpredictable behaviour.
I switched to original Balling method and only use TM A and K for traces now (recommended by Randy) and things seem to have improved.
Before that I played with light, flow etc…
Just an opinion, good luck.