85 percent calcium saturation and 8 percent magnesium saturation is enough in your soil, then apply epsom salt week 3 and possibly 5 on a 10-12 week flower cycle. If you're vegging them, every 3-4 weeks one tsp per gallon of water for epsom salt should suffice, if you need more add more frequently, if you let them root bind in the pot of that soil you will need it more often.