No wonder your fish are dying, you've way too many fish and way too small of a tank... If it's possible, take them back to the fish store. My guess is that your fish are dying from a combination of bad water quality and aggression (you had a clown trigger in a 2 gallon tank with 14 other fish
) Take all of the fish back, research how to properly take care of marine aquariums, and try again once you feel you're ready, really ready. Not trying to be rude, but there's no way that tank is going to last much longer the way its set up and with that number of fish in it...