I really think you need to read more... You are supposed to top up with freshwater, not saltwater, because the water evaporates without the salt and the salinity will increase in your tank when the water evaporates if you add more saltwater, it becomes saltier and stressing/killing the fishes and corals..
Yes bascially, you are cycling with your fishes and corals, sadly expect to see more death until the ANN cycle is over..