in general I try the EI method with 50% wc once per week. I dose 7.5 from KNO3 and 7.5 from my water change. So I add 15 ppm weekly. If I have 2 ppm consumption per day, my plants take 15 ppm per week. So is it logical the 10 ppm of NO3 I found at the end of the week by test, to be the rest from nitrogen cycle??