Well, serves me right for trying to save money. The corals that got the angriest after yesterdays water change all look like they're done for.
I know there have been swings in parameters lately, but everything before the water change was healthy and growing. within seconds of the cloudy new water from that salt mix entering the display, this happened:
Overnight some acros have bleached out completely, some have browned out, and others have taken on a crusty appearance to their tissue that I've only seen preceding STN.