Maxi jet did not kill the fish, unless there was an exposed wire, which would kill everything at exactly the same time. Also sorry to hear about your fish, I've killed a lot of fish too before I learned, but don't let that discourage you. Definitely try to learn what caused it, the best way to do it, is post up the pictures, describe your system and parameters, the age of the system , temperature, salinity, size of the tank, and basically anything you can think of . Some of the guys on the forum are insanely good with identifying the problems with the fish, and they will be able to tell you the most likely cause of death.
From the looks of the tang it is definitely starving, and that usually happens in 2 cases , either 1 you do not feed the fish at all , or the fish is sick and does not eat enough. For the reference, this is a healthy sail fin, they should look this fat even when they're 3"-4" in diameter.
Also , read up on 1) fish diseases, and 2 ) quarantining the fish . both of those things could be found on this forum or on the web. This will save you a ton of money and time.