first of all can you take back the fish that you bought today
second does this gel say that it removes chlorine chloramines and nuetralizes heavy metals
third you should really buy a ph, ammonia, nitrIte, and nitrAte, test kits as soon as possible.
Your fish are producing ammonia. There will soon be bacteria in your filter that will break down ammonia into nitrIte. then another form of bacteria will colonize your filter. They will break down the NitrIte into NitrAte. Nitrate is relatively harmless but should be kept below 40ppm. You can keep down nitrate by having live plants and performing 25% waterchanges bi-weekly.
First your tank will experience an ammonia spike, then a nitrite spike, then as your nitrates build up your ammonia and nitrite will reach zero, this means that your tank has cycled. You should perform 1 gallon water changes every day until your tank has cycled. This will help your fish cope with the poisons in there water. You almost deffinitly will lose fish over the next two months.
Look into BIO Spira
BTW don't feel too bad it happened to me but much worse.
edit: welcome to the fish forums btw, It's nice to meet you and feel free to ask any questions that come to mind.