7 Most Common Cannabis Deficiencies and How to Fix Them

Cannabis plants are hungry for nutrients—but not just any nutrients, and not at every stage. When something goes wrong in the feeding process, your plants will show it—often with strange leaf colors, curling, spotting, or slowed growth. Learning to spot nutrient deficiencies early is key to saving your grow and unlocking the full genetic potential of your plants.

In this guide, we’ll walk you through the most common cannabis deficiencies, how to recognize their symptoms, what causes them, and how to correct them quickly. Whether you’re feeding a tent full of autos or growing elite genetics from Mavericks Genetics USA, diagnosing deficiencies is a must-have grower skill.

Why nutrient deficiencies happen in cannabis

Cannabis nutrient deficiencies aren’t always due to underfeeding. Often, they’re caused by:

• pH imbalances blocking nutrient uptake
  
  

• Overwatering or underwatering
  
  

• Poor soil quality or depleted coco/hydro nutrients
  
  

• Root damage or pests
  
  

• Nutrient lockout from salt buildup
  
  

That’s why the first step in fixing a deficiency is testing your pH and reviewing your feeding schedule.

1. Nitrogen (N) Deficiency

Symptoms:

• Yellowing of lower, older leaves
  
  

• Leaves drop off if untreated
  
  

• Pale overall plant color and weak growth
  
  

When it happens:

Early to mid-veg stage

Fix:

• Increase nitrogen-rich nutrients (especially during veg)
  
  

• Check runoff pH: should be 6.0–6.5 in soil, 5.5–6.1 in hydro
  
  

• Don’t overcorrect—excess nitrogen can lead to toxicity
  
  

2. Phosphorus (P) Deficiency

Symptoms:

• Dark green or purplish leaves
  
  

• Stunted growth, weak stems
  
  

• Red or purple stems
  
  

• Bud development stalls in flowering
  
  

When it happens:

Late veg or early flowering

Fix:

• Use a bloom booster with high P
  
  

• Flush and reset nutrient levels if pH is too low
  
  

• Ideal pH: 6.2–6.5 in soil, 5.8–6.2 in hydro
  
  

3. Potassium (K) Deficiency

Symptoms:

• Leaf tips burn and curl
  
  

• Yellow or brown spots on older leaves
  
  

• Buds appear small and underdeveloped
  
  

When it happens:

Early to mid-flowering

Fix:

• Supplement with potassium-heavy bloom nutrients
  
  

• Check pH: below 6.0 can lock out potassium
  
  

• Consider using kelp or seaweed extracts
  
  

4. Calcium (Ca) Deficiency

Symptoms:

• Brown spots on leaves
  
  

• Crispy edges or distorted growth
  
  

• Slow root development
  
  

When it happens:

Throughout the grow, especially with RO or soft water

Fix:

• Add Cal-Mag supplement
  
  

• Maintain pH: 6.2–6.5 in soil
  
  

• Avoid overwatering—damp soil affects Ca uptake
  
  

5. Magnesium (Mg) Deficiency

Symptoms:

• Interveinal chlorosis (yellowing between veins)
  
  

• Affects lower leaves first
  
  

• Leaf edges curl upward
  
  

When it happens:

Veg into early flowering

Fix:

• Add Epsom salts (1 tsp/gal) or a Cal-Mag product
  
  

• Raise pH slightly if too acidic
  
  

• Be patient—Mg takes a few days to show results
  
  

6. Iron (Fe) Deficiency

Symptoms:

• New leaves turn pale yellow or white
  
  

• Veins remain green
  
  

• Stems may become thin and brittle
  
  

When it happens:

Usually during early veg or after transplant

Fix:

• Iron chelates (Fe-EDDHA) are effective
  
  

• Adjust pH to 6.0–6.2 for better uptake
  
  

• Avoid cold root temps and overwatering
  
  

7. Zinc (Zn) Deficiency

Symptoms:

• Leaf tips discolored or deformed
  
  

• New growth is small and thin
  
  

• Interveinal yellowing at leaf tips
  
  

When it happens:

Mostly in early veg and early flower

Fix:

• Apply micronutrient supplement with zinc
  
  

• Maintain optimal pH
  
  

• Avoid overwatering and compaction around roots
  
  

Deficiency chart for quick reference

How to prevent cannabis deficiencies

• Use high-quality, balanced nutrients made for cannabis
  
  

• Check pH regularly (especially runoff)
  
  

• Don’t overfeed or overwater
  
  

• Keep a grow journal with feeding schedules
  
  

• Flush with clean water between feedings to prevent salt buildup
  
  

Pro tip: The better your genetics, the better your plant’s resilience. At Mavericks Genetics USA, our feminized seeds are bred for strength, structure, and nutrient uptake—helping you avoid problems before they start.

Know your leaves, save your harvest

Most cannabis deficiencies start with subtle changes in the leaves. By catching the signs early and understanding what each nutrient does, you can correct issues quickly and protect your yield.

Whether you’re growing in soil, coco, or hydro, healthy plants start with balanced nutrition and smart monitoring.

Looking for seeds that thrive in tough conditions?
Explore Mavericks Genetics USA for high-performance strains bred to deliver results, even when the grow gets tough.