Hiya Goldie,
It can be hard for us to make a diagnosis over a forum sometimes, the more information you give us on your tank the better it is and the more likley you'll be to get a good helpful answer from us.
Can you please tell us how big the tank is, what fish you have in it, how you prepared it before adding fish, what make of test kit you are using and weather it is liquid based or the paper strips, how long the tank has been set up, which fish have passed on and what symptoms they have shown and what you are doing for maintenance.