Tank is crashing :(

[MitchM]

A few years ago I posted a link to a study done that demonstrated corals are more resiliant when raised in an environment that had varying temperature.
The takeaway from the study was that corals need to be raised in varying conditions from the start if they are to survive varying conditions in the future.
Established corals raised in tight parameters did not survive when subjected to the new varying conditions.

One of the consequenses of aquarists trying to maintain long term success with corals by maintaining rock steady lighting, water chemistry and temperature is that when corals raised in a steady environment are subject to changes in those parameters, the corals are not strong enough to survive those changes.

In nature, corals are subject to environmental changes including lighting, salinity and temperature.
Our commitment to keeping corals within tight parameters produces fragile corals.

The best you can do for your corals is learn what conditions they were kept in previously and don't let your tank conditions wander too far from those conditions.
It's neither easy nor simple to do.