Oops! High CO2 plus low light. This is an imbalance which often causes
algae
soup.

I would disagree here. I have never heard of anyone implicating CO2 in
algae issues. More is better, even for low light tanks, the same can likely
be said about potassium. In fact, Tom Barr's recommended levels work great
on low light tanks... you get into problems when you're below those levels
and light is too high. I must agree however, not enough light.

In any case, Plants cannot grow without Nitrate with an A, as it is an
important
macronutrient. Given that you are dosing micronutrients such as Fe, you
are
probably creating a substantial imbalance.

I believe she's seeing NO2 because her plants are rotting away due to lack
of light. NH4 should not even get a chance to be converted to NO2 if light
levels are okay.

Regarding your KH and pH, these are probably not your problem, although it
would
be interesting to know where all that KH is coming from. What kind of
substrate
and stone is in the tank?

Recommendations: Your light level is too low for a CO2 tank. Either stop
injecting CO2 or double your lighting.

Again, as above, I think this is bad advice. Do increase lighting to keep
plants alive, no need to stop CO2.

Cheers,
Jeff Ludwig