[nereefpat]

In order to keep corals alive, you should have an understanding of testing for, and in most cases dosing, at least alk and Ca. Your calcium is not 1.03 ppm. I suppose that it's possible for alk to slip to 1.7 meq/L (<5 dKH) if you never do water changes or dose for alk.

There probably isn't a need to break down the tank. Just do water changes, or even 1 very large water change, until your parameters are closer to natural seawater:

Temp 75-80
S.G. 1.026
Alk 3 (8dKH)
Ca 400-450