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Also searched as: “lockout symptoms”, “overfeeding signs”, “CalMag ratio”, “EC too high/too low”.
At-a-glance guide: symptom check (deficiency vs. overfeeding), drain diagnostics, Ca:Mg balance, safe corrections — plus real-world examples & FAQ.
The essentials in 30 seconds
- Deficiency: underfeeding (e.g., nitrogen → pale leaves; Ca/Mg → pinpoint necrosis/corking).
- Overfeeding: salt stress → tip burn, very dark leaves, clawed tips, pH shift & lockouts (see recognize overfeeding).
- Ca:Mg ratio: target ~ 3:1 to 4:1. Too much Mg (Epsom salt) can block Ca → “deficiency picture despite adding Ca”.
- Check drain: pH < 5.5 is critical; high EC signals salt buildup. Measure first, act second.
- Correction: rebalance the solution (reduce Mg, modest CalMag), gentle flush only with clear salt overload.
Decision tree: deficiency or overfeeding?
- Measure drain EC: clearly elevated? → overfeeding more likely. Normal/low? → check deficiency.
- Leaf appearance: pale/yellowish, thin → deficiency. very dark green, burnt/clawed tips → overfeeding.
- Drain pH: < 5.5 or unstable? → possible lockout from salt stress.
- Recent actions: Epsom/CalMag added? After stress (pruning/transplant) do not ramp nutrients aggressively.
Nutrient deficiency vs. overfeeding
Differences in symptoms, readings & first aid.
Deficiency
- Pale leaves (N); specks/corking (Ca/Mg/K)
- Growth stalls, weak shoots
- EC normal/low; pH usually within range
Overfeeding
- Very dark leaves, burnt/clawed tips (tip burn)
- Salt crusts on pot rim, frequent wilting despite watering
- Drain EC high; pH may drift (< 5.5 is critical)
Comparison table
| Criterion | Deficiency | Overfeeding |
|---|---|---|
| Leaf color/tips | Pale/yellowish; necrotic specks (Ca/Mg/K) | Very dark green; burnt/clawed tips |
| Growth | Stalled, thin shoots | Stalled despite “fullness”; wilts fast |
| Drain EC | Normal/low | Clearly elevated (salt load) |
| Drain pH | Often in range | May drop (<5.5) or swing → lockout |
| Cause | Underfeeding / off ratio | Too concentrated feed / salt accumulation |
| First aid | Raise feed slightly, check ratios | Dilute/remix feed; gentle flush if needed |
Practical diagnostics: measure drain, watch pH & Ca:Mg
- Drain pH: below 5.5 is critical (lockouts). Typical soil target ~6.2–6.5.
- Drain EC: high = salt load → check recipe first; avoid “full flush” unless necessary.
- Ca:Mg: aim for 3:1–4:1. Too much Mg (Epsom) can block Ca (deficiency look despite adding Ca).
- Pot-to-pot variance: differing drain values indicate uneven substrate/uptake.
In practice, not every symptom equals deficiency or excess. Only the combo of drain numbers, Ca:Mg balance and overall plant health tells you whether to feed or ease off. Measuring first prevents panic flushes and brings balance faster.
Mark (Cannoptikum Crew): “If the tips are burning and the drain EC is yelling, ‘more nutrients’ rarely helps. Drop Mg, nudge CalMag, remix, then measure — funny how many ‘deficiencies’ vanish on their own.”
Overfertilization is not limited to macronutrients – boron, zinc, iron, copper and manganese can also accumulate quickly. Learn more here: Micronutrient Overfertilization.
Diagnostic checklist
- Visuals: pale/dark, burnt tips, specks/corking
- Measure drain: pH & EC (log per pot → spot differences)
- Recent actions: Epsom/CalMag? Pruning/stress? (After stress, do not increase feed!)
- Remix feed: target EC, pH, Ca:Mg ~ 3–4:1
Real-world case
Case: Clear Ca deficiency (pinpoint necrosis) despite CalMag. Drain pH dropping, EC elevated. Recipe also contained Epsom (Mg) — ratio ~2:1 → Ca blocked.
- Action: remove Epsom, slightly increase CalMag, keep base nutrients moderate, remix.
- Result: tips calm down, new growth healthy. Only mild/targeted flush, no “flooding”.
Fixes: safe corrections
If it’s a deficiency
- Raise feeding slightly, verify ratios (Ca:Mg, N:P:K)
- Supplement targeted nutrients — don’t raise everything
- Watch new growth (old damage won’t heal)
- Read more: Deficiency overview
If it’s overfeeding
- Dilute/remix feed, respect target EC
- Reduce Mg, keep Ca modest → 3–4:1
- Gentle flush only with clear salt load (drain EC very high)
- Read more: Recognize overfeeding
Nitrogen Deficiency
Prevention: keep growth stable
- Moderate EC, regular drain checks, keep pH in range
- Watch Ca:Mg long-term (3–4:1); dose Epsom sparingly
- After transplant/pruning, ramp up slowly — no “turbo”
- Stable climate & airflow → better nutrient uptake
Cannoptikum Crew – Conclusion
Measure first, act second: drain pH/EC & Ca:Mg tell you whether it’s truly a deficiency — or an overfeeding lockout. With a clean, rebalanced solution, many “deficiency pictures” resolve without radical flushing.
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FAQ – short & clear
Short: Burnt tips/dark leaves but “deficiency look” at the same time — plus high drain EC & off pH.
Long: Salt overload shifts pH and blocks ion uptake. Result: classic deficiency symptoms despite adding nutrients. Confirm via drain test and rebalance (lower Mg, modest Ca, respect target EC).
Short: Only with clear salt load (very high drain EC). Often a fresh, rebalanced feed is enough.
Long: Heavy flushing can disrupt pH and microbiology. Better to correct the recipe and flush gently if needed. Then re-check drain and feed cautiously.
Short: Target 3:1–4:1. Use Epsom (Mg) sparingly, add CalMag modestly.
Long: Excess Mg displaces Ca on exchange sites — causing Ca deficiency symptoms. Recalculate feed, reduce Epsom if needed, compensate with CalMag. Verify via drain readings.
Short: Check pH & Ca:Mg. A lockout can mimic deficiency despite low EC.
Long: With pH drift <5.5 or too much Mg, uptake is blocked. Fix pH range, reduce Mg, add modest CalMag, remix, re-test.
More guides in the “Grow issues & problems” cluster are in Training methods & grow knowledge and the hub Cannabis seeds explained – tips 2025.