What was the name of the product that came with the kit? Most fishkeepers feel that anything other than BioSpira is generally useless. Unfortunately, the fish stores are in business to sell product and if they don't carry the BioSpira, they'll sell you whatever they have. Truly knowledgeable fish stores will take the time to explain the process to their customers and guide them to the products available to them that would work best. Unfortunately it seems that these stores are few and far between with most of the employees having limted knowledge of fishkeeping. One of the beauties of this site is that we all have varying degrees of experience so there's always someone to provide you with good information.
Next, you might want to switch from using test strips to using the liquid kit that most of us here use and recommend. It is by
API. Aquarium Pharmaceuticals Inc. Freshwater Master
test kit. The reason is that test strips are notoriously unreliable and are expensive. Part of the reason the fish store uses the strips is that they're more convenient than the liquid test kits.....Petsmart.com usually has a decent online price and generally honors that price in their stores. I started using strips - good ones - and when I switched to the same kit the fish store uses I was shocked at the degree of inaccuracy that the strips had.
The tank, although having the chemicals that it came with in it, is not instantly cycled. The fish you added will help the process along, but if the water is not properly treated, the fish will feel the effects of the cycle and may not make it through to the end. It could very well be that the fish you've added are stressing already.
Folks here recommend a product called Prime. Prime treats the water making
ammonia and chloramines in water non toxic to fish. It also binds up
chlorine and heavy metals in water that can cause stress to fish. It may take the cycle a little longer to complete, but the fish would be happier. You'd still have to perform water changes to get through the cycle.
I hope I helped. I know there are plenty of others here that will provide you with any information I may have left out. Good luck!