Depends what medium , if soilless/ light mix, id only be giving it once or twice in week 3-5 depending on strain but usually week 4 flower. I use as directed , canna mono nutes are excellent. If in coco every feed you need cal/ mag really. Same in hydro or any inert growing process, a lot depends on what nutes you use too, I use bio bizz grow bloom heaven and there's enough in them to not need calmag some strains