If I might, EI would provide three doses/week. Each dose is meant to provide at least 7.5ppm for both NO3 & K to the water column. Here is a link that might further explain what I am trying to say.
GH Boosters are suggested as an alternative to dosing just K2SO4 because GH Boosters contain mostly Potassium Sulfate but also provide Calcium and Magnesium - insuring all three of those nutrients are not depleted. What is best - depends on the tap water. As Tom points out, he has not used GH Boosters for several years without any issues.