Al I don’t think you need to worry about water changes affecting your results. At this time. I am sure you have being changing your water regularly and still maintaining a constant reading of nitrates. When you see a rapid decline in nitrates it will be due to the dosing if all other maintenance remains the same.
My own personal observations.
As my nitrates started to diminish I noticed no increases in protein skimmer production. What I did notice was a accumulation of a white viscous material on my prefilters going from my overflow box to my refug.
A short time after my nitrates reached zero there was an accumulation of thick mucus like film floating in my refug. (4inch sand/mud, caulerpa, pods, shrimp, cucumber, snails est.)
After a week or so at zero I had an increase in nitrates to what I estimated to be 2 and they remained at that level with a prophylactic dosing of 2 ml a day. I would remove the layer of mucus like product weekly from my refug.
Note I had some caulerpa die off with the dosing which I attribute to the dosing out competing it for nutrients, that in its self is a testament to how powerful dosing can be. I did not with the die off of caulerpa experience a sexual event associated with it.
I have no explanation for the accumulation of heterotrophic bacteria in my refug that the dosing stimulated and which assimilated nitrogen in their living biomass. But it was constantly in that area where it was harvested