AsNoriuanswered grow question 3y ago I wanted to point out, in soil is better to raise you pH a bit, closer to 6.5 for best calcium absorption and you drop it even more !!!
Never grew in hydro, but it's not first article and all say that Cal mag should be fed in 6.0-6.2 in case of trouble. Later you return to your normal / neutral for all elements pH.
All the Best !!!