Fish are not likely to die from overfeeding, unless you gave them 1/2 can of food all at once. Before figuring out what killed the fish, you do not want to add more, especially after the other fish died and polluted the tank, new ones will just die.
The original was "I killed my parents", then continued with "fishtank" when you opened the thread. It was pretty funny if you had enough of a sense of humor to realize that very few people would kill their parents and then make a thread about it. I saw it, knew that it was a cheap attempt to get people to click on the thread, and didn't take it seriously. Not sure who it offended or why.
If you are willing to go to the expense of buying new fish anyway, why not simply explain what happened to your parents and offer to pay for replacement of the fish?
update: called FGallery, had the tank assessed. They said the tank had a virus/fungus of some sort and they recommended my rents leave it empty for a while when they treat it. Also, the tank was infected before I got there so my ass wont be wooped.