Sorry to hear about your loss. I hope you find the culprit and save your corals. One parameter you didn't mention is salinity. Could that be off?
Tom
That was an issue I had and never really figured my refractometer would be off......it started to cause stn in a few of my acros and most were ones I had in my care for sometime. A couple went total RTN and died before I found my salinity was 1.030+
Sorry to hear about your loss. I hope you find the culprit and save your corals. One parameter you didn't mention is salinity. Could that be off?
Tom
Good suggestion. I would calibrate my refractometer and test. If you don't have calibration solution bring your refractometer by the store and I will calibrate it for you.