What must be the target levels of each minerals in the planted tank then?
Nutrients alone do not grow plants.
CO2/Light, plant type, other sources such as the sediment, the fish waste , algae eaters all play much larger roles in some/all cases.
So you need to ask more questions, how much light, what is the goal of the tank, do you want CO2 and faster growth etc.
Only then can you start thinking about levels really.
A residual level(ppm's etc) in the tank is really not telling if the plant gets enough to be semi limited or non limited for growth.
You could add ferts 3x a day at very low levels, or add them 2x a week at high levels, or none at all with a non CO2, maybe once every 2 weeks etc
If you have rich nutrients in the sediment, no really dosing at all.
PMDD is about 13 years old or so. Folks used very low light and lower CO2 back then.
So they use less nutrients/CO2 etc.
We also add a lot more PO4 today.