It may be worth mentioning your experience to the shop where you bought them from, you never know , it could stop them giving other people the advise they gave you . You are finding out the hard way why tanks should be cycled properly before fish are added.Keep up with the water changes and good luck. I promise it is a great hobby if you do things right and you can always find the right info here from people who don't just want to take some cash off you.