I add about 45 ppm a week of NO3, as KNO3 to my 120 and 180.
The tanks are very well fed with lots of fish.
As the tanks also have high light and a lot of stem plant cover, this ends up runnign about 10-20 ppm a week.
Can I add more without issues? You bet.
Does it help or hinder the plants to do so? No.
I have some so called "fussy" plants. I see little use in adding more NO3 and little improvement beyond this amount for most any light or CO2 level as an upper bound. I think 99.5% of all other planted tanks will use less than this rate.
But...if I do add more, I've never once found any negative issues with plants independent of other factors. I have some client's with automated dosing, they would fiddle with things, then the next day the entire 2 week's worth of ferts would end up in the aquarium. I never got any algae bloom, fish, plants etc were fine.
I see no evidence in research(Gerloff 1966) or within my own experiences and eyeballs that suggest that 40-80 ppm is "bad", but I see no need to go that high on purpose either.
Another way to test the effect is with hydroponics, since the light and CO2 will easily be non limiting, thus independent. This is different from aquariums, but aquariums can vary greatly for light and CO2, and those 2 things cause DRAMATIC differences in terms of growth, nutrients as long as they do not too limiting have little effect if those two main players are addressed.
Focus there, dose less(assuming your readings are calibrated and correct), check the test kits, watch the plants, fish much more. EI is a starting point, you can easily reduce it down as you see fit till you see a negative plant response (not algae!!!). Algae are not limited by plants ferts no matter how lean you dose. Their needs are 1-3 orders less than common aquarium levels.
For new people, it's hard to know what to look for(I had no clue way back when), but nice pics of healthy plants will give an idea of what to strive for.
It is also good idea to post pics of the set up, the tank etc. People often over look something or have a specific goal in mind. Pics are good for that reason.