Sorry, my bad, I didn`t make myself clear "Take this with a pinch of salt" means don`t take this as Gospel truth,
not that you should add sodium chloride.
However Epsom salts can be added to sort out mag def, half a teaspoon to a couple of gallons works wonders, I almost always get mag def otherwise (I`m pretty sure about that
) but I`m not sure what exactly you can use for cal def but I`d wager if the additive you could get for soil is water soluble (surely it is) then it would work fine although I`d only recommend low dosage (less than the given rda anyway).
Just 1-1 1/2 months is a long time to let them grow out with a deficiency and they look so good otherwise.
And yes I`m sure you`re right a build up of unwanted salts would definitely cause difficulties in absorbing certain nutes and minerals.