StrainSpotter · Plant Doctor

Cannabis Leaf Deficiency Chart

Yellow leaves? Brown spots? Curling tips? Match the symptom below to the cause — and the exact fix. Or skip the guesswork: snap a photo and let Plant Doctor diagnose it instantly.

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Deficiency symptoms at a glance

NutrientWhat you seeWhereThe fix
Nitrogen (N)Even pale/yellow leaves, whole plant lightening, slow growthLower/older leaves firstFeed nitrogen (veg nutrients / fish emulsion). Common in weeks 3–4.
Phosphorus (P)Dark blue-green leaves, purple/red stems, brown blotchesLower leavesBloom nutrient with P; check pH (lockout below 6.0 soil).
Potassium (K)Yellow/brown scorched leaf edges, curling tipsOlder leavesPotassium-rich bloom feed; flush if salts built up.
Calcium (Ca)Brown spots with yellow halos, twisted new growthNew/upper leavesCal-Mag supplement; raise pH toward 6.2–6.5.
Magnesium (Mg)Yellowing between veins (veins stay green)Lower leavesCal-Mag or Epsom salt (1 tsp/gal); check pH.
Iron (Fe)Bright yellow between veins, veins stay dark greenNew/top leavesLower pH to 6.0–6.3; iron unlocks. Rarely a true shortage.
Sulfur (S)Uniform pale-yellow new growth, slowUpper leavesCal-Mag/Epsom often covers it; verify pH.
OverwateringDroopy, puffy, dark leaves; slow dry-backWhole plantWater less often; let top inch dry; ensure drainage.
Nutrient burnBrown, crispy leaf tips pointing upTips firstFeed at half strength; flush with pH'd water.

The #1 mistake: it's usually pH, not the nutrient

Most "deficiencies" are really lockout — the nutrient is in the soil, but the wrong pH stops the plant taking it up. Before you add anything, check runoff pH: soil 6.2–6.8, hydro/coco 5.5–6.2. Fix pH first, wait a few days, then feed only if it hasn't recovered.

Not sure which one it is?

Symptoms overlap — nitrogen fade and magnesium loss both yellow the lower leaves. StrainSpotter's Plant Doctor reads your photo and tells you which, with the fix.
📷 Snap a sick leaf, get the fix →
Then re-scan in 7 days to track the recovery.

Quick answers

Why are my lower leaves turning yellow?

Most often early nitrogen hunger (even, pale) or magnesium (yellow between green veins). Feed accordingly and check pH.

Why are the tips of my leaves brown?

Usually nutrient burn (too strong a feed) or potassium issues. Ease off nutrients and flush with pH'd water.

New top growth is pale — deficiency?

New-growth problems point to calcium, iron, or sulfur — often a pH lockout rather than a true shortage.