ersonally i add AT LEAST 5ml/G call/mag to every rez/feeding until week 4 of flower; i'll add up to 10ml/g if the plant likes to eat cal/mag (ala og kush or chemdogD) or i want to add a little bit more nitrogen to the mix since cal/mag is 2-0-0.
i generally like the results when feeding at 50-75% of the manufactures suggested dosage (for all nute products)...
how are you plants doing? are they lush and green or are they minda pale? the plants wil tell you wnat they need/want