Dump the test strips.
Get liquid test kits (API, Read Sea, Salifert) and learn to do your own tests. You should be testing weekly at a minimum.
So obvioulsy something is wrong.
It's either the fish you are getting (I trust very few lfs
to get livestock from)
Or, the way you are handling a/o acclimating the fish
Or, something with your tank.
Was this a brand new tank?
Was it ever cleaned with chlorine?
Is ammonia ever used in or around the tank as a cleaning product?
Tell us everything about the tank, where it came from and how long you've had it.
Have you tried mail-order from liveaquaria, bluezooaquatics or others with 15 day live guarantees?