5 neon tetra have died?

You don't really give a lot of information, but I'll try to answer anyways. Was your tank cycled? If you did not cycle the tank then that is probably the cause of why your fish are dying, and if you get more they will continue to die. Cycle first. Also, 10 fish to add in one day is a lot. You should only add a couple fish at once or it will cause a huge ammonia spike that could kill the fish, especially if your tank is not large. Last, neon tetras are active fish and should be in at least 15-20 gallons, so if your tank is smaller than that, it could have contributed.