If..........the tap does have 3-4ppm from their analysis, (not your test kit unless you calibrated it), then you likely can not dose PO4 at the water change day.
More PO4 will not hurt, but you might not need it.
GH booster is a fair amount of K2SO4.
You can add K2SO4 instead after a water change only.
Mg might be light even if the GH is 11 etc, so check that tap water report.
You might just add a little MgSO4, epsom salt, after a water change etc.......
Then avoid GH booster.
You can dose every other day or cut the amounts in 1/2 and dose daily, whatever routine works for you. It's not written in stone.
Just the idea that you dose frequently(whatever fequency is good for you depending on the growth rates/light intensity), then do a good sized water change to reset the tank at the weeks end.
Nothing more really.
Targetting those ranges should be relatively easy as long as ou keep a good eye on the lants and make sure they are growign well, good CO2...........moderate to low light etc. Light and CO2 are more crictical and will cause more issues for folks than nutrients.
So pay attention to those more.