Reverse osmosis with super soil pH and ppm

Hey now,
Reverse osmosis and how to use it with super soil.
Just got a drilled well and it tested high in iron and manganese. so we got a reverse osmosis machine. 300 gpd hydrologic.
Water comes out of ro machine at 0 ppm 5.4ph so do I add cal mag? Do I pH? In what order? I have read so many conflicting posts. Did give plants in flower a low dose of cal/MG and ph'd to 6.1, 2 waterings ago Currently running no cal MG supplement and hoping there is enough in the super soil to take care of business. Plants were lacking in some direction.
So how long does the MG last in super soil?

I would personally pH up from 5.4 for soil, though if you’re using RO water, it’s really kind of irrelevant because the pH will be easily influenced as it interacts with the soil. Soil acts as a buffer, and there’s little to no ions within RO water. As an example, see what happens when you add 1 single drop of pH up to a liter of RO water —- the pH will change quickly.

On to your question about adding cal/mag, I’d really like to figure out what other people do as well for RO + soil.