nutrient schedule

My question is: since the soil is moist not wet or real dry, and I recently watered my plant should I wait until the soil is more on the dry side before I give the Flora Series Nutrients? Today is the scheduled time for them. My plant is in the 3rd week of Flowering..(Hindu Kush)

How ofter do I give my plant Cal Mag The bottle only says the amount

My grow tent is only 2x4x5 ft tall so I think my best option is to put the plants in rockwool blocks in a tray on the floor and drip feed on a timer. What size rez should I use, so I'm not wasting water & nutrients?? Also, is there a feeding chart I could go by?