potassium
you’ll generally see symptoms on older leaves, but not always. Sometimes you’ll see the symptoms at the top of the plant. Leaves with a potassium deficiency get yellow, brown, or burnt tips around the edges and tips. The burnt edges may look a little like nutrient burn, except the affected leaves also start turning yellow in the margins.You may see the brown burnt edges first, or you may see the yellowing first. When the leaf symptoms are both present, it’s a good sign you have a potassium deficiency in your leaves.
Plants may stretch and stems may become weak, but leaf symptoms are more noticeable. The leaf symptoms appear somewhat similar to an iron deficiency in that they can turn bright yellow, but the tips of the leaves curl as the edges turn brown, burn and die.Sometimes the burn can appear pale, bleached or yellow, instead of brown. If you look in the background of this pic, you can see some of the leaves have turned brown in addition to the bright yellow leaf in the front. These are all signs of a marijuana potassium deficiency.
Sometimes a cannabis potassium deficiency (like all deficiencies) can be triggered by stressful conditions (for example overwatering, heat, transplant, etc) and may clear up on its own after the period of stress is over.
