You don't flush a living soil or super soil.
That's for a different style grow. You have a soil you don't add things to, so you don't flush stuff out.
With this soil all the nutes they need are always available, they take what they need when they need it.
No cal mag, no nutes or supplement needed. If you "run out" of nutes in a super soil, it is because the plant broke down all the soil so giving it nutes or cal or mag won't help, they, at that point, won't be able to drink because the water will run straight through it because no soil to hold the water.
People don't think about soil right, it's not like hydro, the dirt is the nutes. It isn't just what it has in it, it is it's ability to sustain it. You also don't need to ph water when using soil. Soils are usually buffered and make the water the ph it needs to be.
You chose a super soil, use it as it is designed to be used! No flushing, no feedings, no cal or mag... Just water her right.