Like the others have said. Adding eggshells and epsom salts to your soil prior to planting is a great way to introduce calcium and magnesium into your soil. Biobizz indeed do an organic calmag, I have a bottle of this to hand for when needed. Organic Black molasses also contains lots of micro nutes that are very beneficial for soil growers and also tap water sources can contain calcium and magnesium. I noticed since using rain water to feed my plants, I am having to supplement call mag mid flower from the bottle even though I condition my soil with Epson salts and egg shells. Happy gardening 🌱👍