Really good question, suspect you are more scientific than me. I follow the box instructions, using the little spoon, which is one 5 ml to 5 litres for the solution, 750 g box, 5 g spoon. But after that I go really gently. I tend to add only a litre of the solution to my 250 litre tank and test, an hour or so later. That is unless I have previously tested and got a zero test result or noticed signs of deficiency, browning on floating plants seems a key feature of nutrient exhaustion in the water column, assuming the lights are not too hot or intense and simply burning or bleaching them. I absolutely never add more than two litres at one go, I aim for between 10 ppm and 20 ppm of Nitrate, falling within a fortnight to zero. I harvest a lot of floating plants, thus, so long as I don't go above 20 ppm of Nitrate in the water column, I can normally get a zero reading again within a week or two without a water change. As I think I said before I don't follow EI. I absolutely don't do 50% water changes and reset. My water is quite hard, TDS above 250 and KH above 16 and a 50% change is beyond my normal supply of rain water to keep my tank within more acceptable parameters, except of course when it has been very wet, I have two water butts. Also, partly because sometimes, in the summer, I can have more than 20 ppm of Nitrate in my tap water, twice I have measured at least 40 ppm, readings which I know, my water authority would dispute. Such high Nitrate readings will make dosing unnecessary at best, and detrimental at worst. However, the last time I had high Nitrate in my tap water was back in the summer of 2022, it has been wet enough since, to ensure my mains supply has been pretty unpolluted. River extraction when flow is low, is I think the explanation here where I live in Berkshire. I do however, a pretty regular dip test, at least once a fortnight and a proper Nitrate and Phosphate drop test occasionally, the latter maybe every couple of months or if I suspect an issue, I aim to keep Phosphate low, below 1 ppm. I find much above that level for any time and you get an algae problem. I also occasionally test my KH, I try and keep it below 10, ideally below 8, and I use a general dissolved solids metre at least once a week, and after every water change. I aim to keep my main tank at least below 200 ppm total, ideally below 175, dissolved solids. Only if I have high Nitrate or Phosphate do I change more than 10% of my tank water. I also run a small tank, also with injected CO2, water volumes are less of an issue there, and I keep my KH below 6 and TDS below 125. It is thus a little haven for plants. With two LED lights I can grow virtually anything in that tank. However, I will add chelated Iron if I spot deficiencies, generally I use Doff Sequestered Iron, one little packet from the five in the box lasts me a year, when I lived in London and had even harder water to contend with, I used at least two a year on a five foot tank.
Apart from fish food, electricity and CO2, I run my tanks for pennies. I use upwards of 15 KG of CO2 however, a year, I could run my 4 foot for less in CO2 but I would have to drop the hardness more. In terms of new plants and fertiliser, I spend almost nothing. In fact my local tropical fish was, for some time, giving me significant credit for decent crypts which easily paid for my fish food, however, of late I have been lazy and been simply composting surplus crypts with floating plants and stem plants.
Really good luck to you but if I have any real, unsolicited advice, after 55 plus years in the hobby, it is to go really gently with any changes to Hardness, CO2 levels, lighting or water column fertilisation, sadly, be willing to euthanize fish when necessary and most importantly and finally, either quarantine fish and or, use a UV, I do both of the latter, nobody wants to have to try and treat disease in a fully furnished, mature and well running tank, and apart from treatments for white spot don't buy any from the shelves of the store, they are all apart from white spot treatment of very limited use.
