RO water + CoCo Brick + Perlite + 5-7 mg of CAl-MAG (p/gallon) per feeding = no issues. You are not competing with pre-added nutes or tap water subjected flood/heavy rain messing up the learned balance.
Of course add your regularly scheduled nutes. Which again, will not OD with pre-added nutes from MANY soil options on the market when using CoCo and Perlite.
With CoCo Brick and Perlite you are wasting time checking Ph on soil. Check nutrients Ph before adding.
Problem: get out your Visa card for RO system. You can buy "in-line" RO filters that connect to a hose within reasonable price range; but not the same.
Otherwise, face a constant struggle to balance your primary and secondary nutes.
Anyone, expert or novice, that has not tried CoCo brick with perlite is really missing out. This is newer, but plants LOVE IT. You will fall in love with the texture. AND you control all primary and secondary nutes.
Vets, please correct me if I am wrong.