Sorry to hear you couldn't get a bigger tank before one of your fish died. This is what we were all worrying would happen. Unless you want more of them dying I'd do something about your overstock issue now. Also, the amonia and/or nitrate levels in that tank are probably through the roof with that many fish in there. I'd be doing a 10% water change every day or two if I were you. Do you check the water perameters? If you don't, you should start doing it and you'll see why its so important to follow the rules for stocking a tank.