Alright ive got a question regarding my nitrate readings.

Thank specs:

75 gallon (65 gallons of water0
ADA AS
CO2 (15-30 ppm)
2 2215

Stocking:

23 Neon tetras
10 Von Rio Tetras
5 Black Phantom Tetras
10 Panda Cories
4 Oto
2 Pleco
~30 RCS

Ive been playing around with my dosing schemes and was dosing this

3/4 kno3
1/4 kh2po4
1/4 trace

I noticed i was getting gsa so i modified it a bit.

1/2 kno3
1/4 kh2po4
1/4 trace

All dosing is done with dry ferts from greg watson:

Now i have been skipping dosing my KNO3 because i noticed my nitrates always seemed to be 15+. Even without dosing KNO3 in the past 2 days my nitrates are still that high. Granted i just cleaned out one of my filters, but is my fish load keeping my nitrates that high? I feed them every other day. So whats going on?