You probably did not acclimate the fish. They could not adapt to the new water in this fashion. Please read the article Thor linked for you. The one on how to introduce new fish to your aquarium. A lot of new fish keepers make the same mistake.
Testing water at this point is quite pointless. While ammonia and nitrite can kill the fish, they do not kill so fast. Died in hours is a sign of shock. It can be easily avoided with proper acclimation.
On the side note, there is no need to take down the fish tank repeatedly. Something in the tank is unlikely the cause, and the fish do not like newly setup fish tank anyway. They like aged water and cycled filter. To help the aquarium nitrogen cycle, you should get a bottle of Tetra SafeStart, but it is something you need to worry about after you get pass the fish acclimation problem.
