In all honesty, I've never used the ammonia hanna checker so unsure how sensitive that it is. With lower quality test kits you want it to read 0...which is why we can usually say non-detectable levels. My only suggestion is to do a large water change and check again to report back with the readings. That should let us know where things should be sitting in the system.
With that said, this is an established system isn't it?