Cannabis needs a balanced and adequate supply of nutrients to grow well and produce high-quality buds. However, sometimes they may suffer from deficiencies or excesses, which can affect their health and yield. Here are some of the most common, and how to distinguish them: Phosphorus deficiency: This is a mobile nutrient that is important for root development, flowering, and resin production. A lack of it causes the lower leaves to turn dark green or purple, and develop brown spots or edges. The plant may also have slow growth and reduced bud formation. Potassium deficiency: This is a mobile nutrient that is involved in water regulation, enzyme activation, and sugar transport. A lack of potassium causes the lower leaves to turn yellow with brown tips or edges, and curl up or down. The plant may also have weak stems, poor resistance to pests and diseases, and low-quality buds. Magnesium deficiency: This is a mobile nutrient that is part of the chlorophyll molecule and helps with energy production. A lack of magnesium causes the lower leaves to turn yellow with green veins, and develop brown spots or necrosis. The plant may also have reduced photosynthesis, chlorosis, and leaf drop. Boron deficiency: This is a mobile nutrient that is essential for cell wall formation, sugar transport, and pollen tube growth. A lack of boron causes the growing tips to die back, and the stems and roots to become brittle and cracked. The plant may also have distorted leaves, flowers, and fruits. Iron deficiency: This is an immobile nutrient that is required for chlorophyll production and electron transport. A lack of iron causes the young leaves to turn yellow with green veins, a condition known as interveinal chlorosis. The plant may also have poor growth, reduced yield, and susceptibility to diseases. See more...