Can you add NEEDED ingredients to SS and let it cook more?

I just got done with a thread asking why the fuck my plants had a Ca/Mg/Fe deficiency in Subs SS, when I mixed the soil to the T.

I use RO water and we all decided it was probably my problem.

When that thread was all said and done someone mentioned that they went back and read Subs recipe and it blatantly says to:
"add 1/2 cup powdered Cal-Mag if using an RO system"

So THE QUESTION IS: I mixed up a half batch of SS about a month ago... ide have to check the date on the bin... anyways I dont need it for another month or so, CAN I ADD THE POWDERED CAL-MAG RIGHT NOW AND LET IT ACTIVATE FOR ANOTHER MONTH?

Or will adding anything at this point change the nutrient composition and PH balance? because it has already been cooking for a month or so...

i see no reason why you cant still add to it...also dont think you would need to give it another month but if u dont need it anyway thats fine..

why are you using ro water? in most areas of california, or at least southern californa all of the local reservoirs are state parks where the water is kept in a thriving ecosystem and nobodys allowed to pollute it. you can fish, hike, but not swim or let the dogs swim.

I just use a hydrologic smallboy and it doesnt waste water like a ro machine, removes the chlorine/chloromine/and hard minerals but leaves the water like great well water.