How I mix my nutrients.
Regular tap water. I don't bother de chloronate it.
Check ppm of water (mines usually 150ppm)
600 - 150ppm = 450
450 ÷ 2 = 225ppm
Part A of nutrients I add until the ppm shows 375ppm then I add part B until I hit the 600ppm goal.
Once I have that correct I alter the ph if it's needed using ph down. In soil I aim for about 6.2 ph.