nitrates in kalk water

[kole]

So I've been battling GHA for a couple of months now. It started quickly and the tank is quickly looking like crap. I blame it on the marco rock leaching but thats not what I want to discuss here.
So on my witch hunt to test the things I put in the tank I tested my kalk water that I use in my ATO. I have a container that I dip kalkwater from to fill my ATO instead of adding kalk powder directly to the ATO water container. I got a reading around 15ppm of nitrates and 0 phosphates. I mixed 2 teaspoons of kalk in 2 gallons of new rodi water that I had tested to be 0 ppm of nitrates and phosphates when I later tested the kalk I had around 2 ppm of nitrates.
I used Salifert test kits.

I'm wondering if this is common would some of you that uses kalk in your topoff water test it to see if your getting any nitrates and post your results?

Thanks