Me and my Fish?

Maybe you introduced them to the tank too early? With tropical fish I believe you are supposed to leave the tank set up for around a week so it develops its own environment. Also make sure you are introducing them properly and not just dropping them in. Fish get stressed very easily. You might be better trying to buy them from somewhere else. My local pet shop fish always died within hours of getting them home. Now I go to a proper aquarium where the guy knows everything about fish and makes sure you have all the kit and information before you set up. Good Luck with your next try! x