Your first mistake here and it is a big one! NEVER wash live rock in hot water! You should never need to wash the rock at all. If you do need to remove contaminant from your rock it should be done in a container of saltwater. Live rock is called live rock because it gives the essential bacteria somewhere to live (NEVER EVER EVER DISINFECT ANYTHING in a marine aquarium) as well as any small crabs, and a whole list of other critters. Washing your rock in hot or cold fresh water compounds your initial problem!
Never wash your sand and never wash your rock!
Marine Aquariums are not like a goldfish bowl where you can wash everything!
Even in the event such as what you have had. What you should have done is remove the dead animals, increase aeration leave it over 24 hours (yes I know it stinks) do a 50% water change after 24 hours wait for a few hours and test ammonia, and nitrites if these figures are 0 or close to then you can remove the aeration set up back to normal(otherwise leave it until this happens). Last test nitrate should have a high reading if the cycle has completed unless you have a deep sand bed however a reading above 0 should still be present. Now over a couple of days do 25% water changes until ammonia, nitrite, and nitrates are all at or close to 0.
Leave it for a week testing regularly before adding any fish. Treat it as a new aquarium From this point on only add one to two damsels wait at least a month before adding any other fish and only 1-2 at a time allowing a couple of weeks in between.
Don't use additives to Speed up the cycling process it will occur naturally WITHOUT adding anything. (be patient otherwise it will cost you a **** load of money and you won't get anywhere)
The only additives that you should add since you are making salt water is essential elements calcium etc.