When I run rdwc systems I like my ph at 5.9 on a fresh res. I Top up with half strength nutrients at 5.6-5.7 ph. The ph will usually raise slowly throughout the next 10 days to 6.3.
Rinse and repeat.
In veg
Cheapo A+B nutrient at ~650ppm
Touch of potassium silicate
Good to have epsom salt and cal mag on hand
In flo
Week1 veg nutrients
Week2 50/50 veg/flo
Week3 and on
Cheapo A+B ~900ppm
Week4 slight pk13/14 boost 1100ppm total
5 900ppm
6 800ppm
7 700ppm
8 500ppm
9 300ppm flush
Flawless nuggage every time
There should be plenty of calcium throughout the grow as is. some strains can benefit from 1-2ml/l calmag, maybe 
