If you have a heavily stocked tank, and are therefore adding a lot of fish food that could explain higher nitrates, especially when combined with EI dosing.
I would cut the EI dosing in half and run that for a week or two.
Are you maintaining this as a high tech set up? High light, CO2?
If not, then the lower dosing of the ferts might be just right.
DIY co2, 4 - liter bottles, one changed out every week with a ceramic diffuser. Lights; two T8 - 24 inch 6700 K and one 24 inch T5HO 6500K.
36 Gallon tank. It is stocked well. Can the frequency of changing the filter effected water parameters?