You were lucky to got away with it several times. When I start tanks I usually let it run for a minimum of two months with skimming, minimum lighting before I put any livestock in it. Us in the west have no patience. Tony Vergas at the last meeting told everyone something I already knew. In Europe they let a tank run 90-180 days with no lights or livestock and let the pods and other microscopic organisms in the rock multiply to extreme levels. Then when you turn the lights on and start adding livestock VERY SLOWLY the system is able to handle it.
Sorry to hear about your loss. Re-group, catch your breathe and count it as a lesson learned. Don't let it discourage you.
I've been doing this for 21 years and I could fill a notebook full of all the mistakes I've made in hindsight. The biggest this I've learn is slow, slow, slow, slow, patience, patience, patience. All changes must be made slowly. The ocean doesn't have radical water parameter swing and marine species can't handle that. Some of my corals are recovering from being burnt by LEDs and alk swings so I'm still learning!