I had a single but very bad experiece with Hagen's Phosphate. Besides
the difficulties with discerning the hue of blue the test goes bad and
it starts to show much less Phosphate than you actually have. Mine
was showing 0.5 ppm and I had in excess of 30 ppm, now that's serious.
I'm using a brand new Hagen Phosphate now only until I find a
replacement.

Hach Nitrate is great and very precise. I wish their Phosphate test
was not $134...

pH - nothing better than a digital device.

KH - Aquarium Pharmaceutical does well.
GH - Aquarium Pharmaceutical may be a bit harder to read, the color
change is rather subtle.

Will check out for Lamotte Phosphate now...

--Nikolay