Calcium deficiency in cannabis
What it looks like
New growth comes in twisted, with brown spots or dead tips on young leaves. Calcium does not move well inside the plant, so the top shows it first. Often tied to low pH, soft water, or a root zone that is too wet to take it up.
What usually causes it
Check pH and how wet the pot is. Calcium uptake fails in a soggy root zone. A normal cal-mag product, used at the label rate, is the usual correction once pH is in range. Soft water and coco need it more often than tap water in soil.
Check this first
Brown spots and crispy edges on newer leaves, tips dying. Check pH first. Calcium does not move well into new growth if the root zone is sour or the leaf is under a dry wind. Do not pile cal-mag on a plant that is already burnt.
This is identification for a home grow. It is not a pesticide label and not medical advice. Follow your local law.