Should i add cal-mag now or not ? 4 week old plants in ffhf soil. Bottom round leaves turning yellow and falling off. So that tells me plants are using up nutes in soil. So when i start feeding VERY lightly this week, should i use cal-mag from the start, and maybe always, or not ? I've read it's to balance everything out, but do u need it if nothing is out of balance. Like using it as a preventative ? Which raises another ? Should i be using anything else as preventative measures ? Tks.