Sorry for your loss but I am not suprised. Those fish were not healthy at all, I would avoid buying anymore discus from that store. head over to simplydiscus.com read up on discus keeping and buy some fish from one of there sponsers, either Kenny or Discus Hans.........you will be much happier starting with healthy fish.
I had really good luck with Rocky Mountain Discus and Mac's Discus. All my discus from them are great. Sunrise has nice fish other than he feeds them only Bloodworms.