Sensi grow formulas are up in the 500 ppm range for calcium and bloom the 800 ppm range. Lucas mix is only about 200 ppm calcium so I would not worry about the calcium levels. The bloom is a bit lower in magnesium than I like at 100 ppm, I prefer 150 ppm. But adding just a small amount of magnesium sulfate (ephsom salt) is simple enough to do. It would only take 0.35 grams per gallon of water to kick the Magnesium up to 150 ppm.
The main reason for the large need for higher levels of calcium and magnesium during budding is the need for neutralizing H+ ions (acid) released by the roots and this is done by magnesium carbonates generally. Generally the growers who have signs of magnesium and calcium defiencies during budding are also the same people fighting daily declines in pH. Go figure. You can sfaely assume that if your using AN Sensi and you are not having a large daily decoine in ph, then yu are fine with your calcium and magnesium levels. If you are having a problem with your pH you are likely a little short on magnesium. Sensi has loads of calcium.
Typical signs of a magnesiun deficiency are that the lower leaves yellow, the stems turn red, the leave tips turn white, and necrosis (death) takes place.
This is very typically seen in grows where for some reason the grower with holds nutrients in the last few weeks of budding and say they are flushing the plant of excess nutrients. In reality they are just starving the plant of nutrients during the timewhen the plants most needs nutrients to fill out its sex glands. For plants that normally reproduce seed that is what it is all about. You probably do not see many professioanal sensi growers who with hold nutrients and acll it fluhing. definitely not any that produce buds with high THC levels.