[bertoni]

I agree with the PolyFilter idea. They are cheap, and sometimes help. CupraSorb will remove copper, but the PolyFilter will turn blue if there's much present, thus acting as a bit of a test kit.

I'm a bit skeptical about the Triton results. They have been shown to be inaccurate for at least some trace elements, and their methodology is a bit suspect.

The parameters you have given are reasonable as far as they go, given hobbyist kit accuracy. I might double-check other parameters, such as SG, temperature, and the like. I have had multiple heaters fail, for example.

For coralline growth, you might be seeing some generic issue with the tank, or you might need to import a strain that is compatible with your lighting. When I changed the lighting on one of my tanks from PC to metal halide, I killed off most of the coralline, and it never came back. I was happy about that, but you might want coralline. I'm not sure where you stand on that.