Hello i wanna do a grow using the 2 whole part AN feeding program and on the chart its says to mix the nutrients with 0ppm water.. So i bought a r/o system and now i read that after you filter your water people add cal mag to add calcium, magnesium and iron supplements that is lost? Is this really necessary? if im already adding the whole line up of nutrients and additives do i still need to add cal mag? what happens if i dont?