Wow, I really wish I could help -- that is the worst.
I'd suggest having all your test verified by the LFS
, but at this point, you readings may be off just because of the cycle of events that were triggered. In other words, something dieing may now show as ammonia in the tank, but the ammonia may not have been the initial cause of the problem.
Did you look at your pH when this first happened? Adding kalk
(not via drip) can drive pH down considerably, which could have cause the fish deaths. I'd really look to pH more than a contaminant, as a contaminant would have likely killed inverts/corals first. Then the fish dying could have triggered a cycle which effected the corals, etc.
That's my best guess.
I plan on doing water changes 5 gallons at a time 5 or 10 times today to try & get whatever is in there out..
Less frequent, larger water changes will have more impact on the water quality. In other words, one 20% water change is much better than 4 x 5% water changes. I would strongly suggest changing about 25% of the water today, again tomorrow if things don't look better, then again Friday.
I'd also run some GAC asap
Good luck, keep us posted!