test kits

[Brown_D at pcfnotes1_wustl.edu]

I've got 100% fluorite substrates and the CO2 (pressurized) is up and
running, and the plants are doing a little better, but I have only dosed
micronutrients and an iron supplement.  I suspect my plants may have some
macronutrient deficiencies, like K in particular, and I have only seen test
kits for nitrate, nitrite, ammonia, gH, kH and pH in my LFS.

What other test kits would you recommend, at least as a baseline, to see
what my tanks have now, so I can plan a macronutrient supplement regimen
for them?  I am thinking K and Fe, and don't know where the best source is
for them online.

Thanks for your attention,
Diane Brown