Cannabis Nutrient Lockout Symptoms Database

Quick Diagnostic: Where Is It?

Rule #1: Mobile nutrients show on OLD lower leaves first. Plant steals from old to feed new. Immobile nutrients show on NEW top growth first. Can't move them.

Mobile Nutrients

Symptoms on: OLD LOWER LEAVES

List: N, P, K, Mg, Mo

Why: Plant translocates these to new growth when deficient. Old leaves sacrifice themselves.

Fix speed: 3-7 days after correction

Immobile Nutrients

Symptoms on: NEW TOP GROWTH

List: Ca, S, Fe, Mn, Zn, Cu, B

Why: Once in leaf, stuck there. New growth shows deficiency immediately.

Fix speed: New growth only. Old damage permanent.

3-Step Diagnosis

Location: Top or bottom of plant? New or old leaves?
Color: Yellow, purple, brown spots, burnt tips, interveinal?
pH: Check runoff pH. 90% of lockouts are pH. Soil: 6.0-7.0. Coco/Hydro: 5.5-6.5

Mobile Nutrient Deficiencies

Shows on lower/older leaves first. Plant moves these around.

Nitrogen (N)

Uniform yellowing starting at leaf tip, bottom leaves first

Leaves drop off easily

Slow growth, small leaves

Purpling stems in severe cases

pH Lockout: <5.5 or >7.0

Fix:

Soil: Top dress blood meal or water with 5-1-1 fish. Foliar: 1/4 strength veg nutes.
Hydro: Raise N to 150-200ppm. Check pH to 5.8-6.2.

Phosphorus (P)

Dark green/blue-green leaves

Purple/red stems and petioles

Bronze/purple spots on lower leaves

Slow growth, small buds

Leaves curl down, look burnt

pH Lockout: <6.0 Common in cold soil

Fix:

Soil: Bone meal or bat guano. Raise soil temp >65°F.
Hydro: Raise P to 60-80ppm. pH 6.2-6.5. Cold locks P hard.

Potassium (K)

Yellow/brown edges, burnt tips on old leaves

Interveinal chlorosis moves inward

Leaves curl up, look crispy

Weak stems, stretchy growth

Brown spots like Ca but on edges

pH Lockout: <5.5 or Ca/Mg excess

Fix:

Soil: Kelp meal or langbeinite. Flush if salt buildup.
Hydro: Raise K to 200-300ppm. Check Ca/Mg ratio. Too much Ca locks K.

Magnesium (Mg)

Interveinal chlorosis: yellow between green veins

Starts on lower/middle leaves

Leaves curl up, rust spots

Purple stems

Looks like iron but on OLD leaves

pH Lockout: <5.5 or excess Ca/K

Fix:

Soil: 1 tsp Epsom salt per gal water. Dolomite lime.
Hydro: Cal-Mag 5ml/gal. Foliar: 1 tsp Epsom/gal. Works in 48hrs.

Immobile Nutrient Deficiencies

Shows on new/top growth first. Can't be moved once placed. Old damage is permanent.

Calcium (Ca)

Brown spots on new leaves, look like rust

Stunted, twisted new growth

Necrotic spots, dead patches

Weak stems, hollow

Root tips die, brown

pH Lockout: <6.2 Most common lockout

Fix:

Soil: Dolomite lime or gypsum. Water with Cal-Mag.
Hydro/Coco: Cal-Mag 5ml/gal EVERY watering. pH 6.0-6.2. Coco strips Ca.

Sulfur (S)

New growth turns lime green/yellow

Uniform yellowing like N but on TOP

Stunted growth, thin stems

Leaf tips burn

pH Lockout: >7.0 Rare

Fix:

Soil: Gypsum or Epsom salt.
Hydro: Potassium sulfate or Epsom. Usually enough in base nutes.

Iron (Fe)

Interveinal chlorosis on NEW leaves

Top leaves turn bright yellow, veins stay green

Looks like Mg but on TOP not bottom

New growth pale/white

pH Lockout: >6.5 Very common in soil

Fix:

Soil: Lower pH to 6.0-6.5. Chelated iron foliar.
Hydro: pH down to 5.8. Add Fe-EDDHA. Don't use with high P.

Manganese (Mn)

Interveinal chlorosis + brown spots on new growth

Yellow with necrotic spots

Stunted leaves

pH Lockout: >6.5 or excess Fe

Fix:

Lower pH. Flush if Fe excess. Manganese sulfate foliar 1/4 tsp/gal.

Zinc (Zn)

New leaves small, narrow, twisted

Interveinal chlorosis + rosetting

Short internodes, bushy top

Leaf tips discolored

pH Lockout: >7.0 or excess P

Fix:

Lower pH. Reduce P if using bloom boosters. Zinc sulfate foliar.

Boron (B)

Growing tips die, look burnt

Thick, brittle, distorted new leaves

Hollow stems

Root tips die

pH Lockout: <5.0 or >7.5 Rare

Fix:

Borax 1/8 tsp per gal soil. Very easy to overdose. Use kelp meal instead — safer.

Lockout Causes: It's Usually Not Deficiency

90% of "deficiencies" are lockouts. Adding more nutes makes it worse. Fix the cause first.

Top 5 Lockout Causes

Cause	What Happens	Symptoms Look Like	Fix
pH Wrong	Nutrients precipitate, roots can't absorb	All deficiencies at once	Test runoff. Flush. Reset pH.
Salt Buildup	EC too high, osmotic lockout	Burnt tips, claw, multiple defs	Flush 3x pot volume pH water
Cold Roots	<60°F roots shut down, P locks	Purple stems, P deficiency	Heat mat. Keep >65°F
Overwatering	No oxygen, roots rot, can't uptake	N, Ca, Fe all at once	Dry out. Add perlite. Fabric pots.
Nutrient Antagonism	Too much K locks Ca/Mg. Too much Ca locks K/Mg	Ca def with high K	Balance ratios. Flush and reset.

Mulder's Chart: Antagonism

Too much of one nutrient locks out another:

Excess N →

Locks K, Ca

Excess K →

Locks Ca, Mg, N

Excess Ca →

Locks Mg, K, Fe

Excess P →

Locks Zn, Fe, Ca

Excess Mg →

Locks Ca, K

pH Lockout Chart

pH	Soil - Locks Out	Hydro/Coco - Locks Out	Optimal Range
4.5-5.0	N, K, Ca, Mg, P, S, Mo	Ca, Mg, P	Too Low
5.0-5.5	Ca, Mg, Mo	Ca, Mg	Low
5.5-6.0	Ca, Mg	—	OK Hydro
6.0-6.5	—	Fe, Mn	Optimal Soil
6.5-7.0	Fe, Mn, Zn, Cu	Fe, Mn, Zn, Cu, B	High Soil
7.0-7.5	Fe, Mn, Zn, Cu, B, P	All micros	Too High

Golden Rules:
Soil: 6.0-7.0 pH, sweet spot 6.3-6.5
Coco: 5.5-6.5 pH, sweet spot 5.8-6.2
Hydro: 5.5-6.5 pH, sweet spot 5.8-6.0
Let pH drift 0.3-0.5 through range. Don't lock it at one number.

How to Fix Lockout: Flush Protocol

Step 1: Diagnose

Check runoff pH + EC: If pH off >0.5 or EC >2.5x input, flush.
Check runoff color: Dark brown = salt buildup. Clear = OK.
Check roots: White = healthy. Brown/mushy = root rot.

Step 2: Flush

Medium	Water Amount	pH	Additives	Notes
Soil	3x pot volume	6.5	1/4 tsp/gal Epsom	Slow pour. Last gal: 1/4 strength nutes
Coco	2x pot volume	5.8	Cal-Mag 2ml/gal	Never plain water. Always Cal-Mag
Hydro	Drain + refill	5.8	1/4 strength nutes	Clean res, refill fresh

Step 3: Reset

Wait 48hrs: Let plant recover. No nutes.
Resume 1/2 strength: pH perfect. Watch new growth only.
Old leaves won't fix: Judge by new growth after 7 days.
Foliar if needed: Epsom for Mg, Cal-Mag for Ca, chelated Fe for iron. 1/4 strength.

Never: Flush and then blast full-strength nutes. You'll burn it. Flush → 48hr water → 1/4 strength → 1/2 strength → full. Takes 7-10 days.

Visual Symptom Cheat Sheet

Symptom	Location	Likely Cause	First Check
Uniform yellow	Lower leaves	Nitrogen	pH, then feed N
Purple stems + dark leaves	Whole plant	Phosphorus / Cold	Root temp, pH 6.2+
Burnt edges, yellow	Lower leaves	Potassium	pH, K:Ca ratio
Interveinal yellow	Lower leaves	Magnesium	pH, Epsom foliar
Brown spots/rust	New growth	Calcium	pH 6.0+, Cal-Mag
Top leaves yellow, veins green	New growth	Iron	pH too high >6.5
Twisted new growth	New growth	Calcium or Boron	pH, Ca levels
Burnt tips only	All leaves	Nutrient burn	EC too high, flush
Claw, dark green	All leaves	N toxicity	Flush, reduce N
All defs at once	Whole plant	pH lockout	Flush, reset pH