Official Guide: What’s Wrong With My Cannabis Leaves?
Post Photos — Let’s Diagnose It Together
If your cannabis leaves suddenly look strange, don’t panic.
Yellowing, curling, brown spots, clawing, taco leaves, burnt tips — most leaf problems are fixable once you identify what’s actually driving them.
This is a live diagnosis thread. Post clear photos and your grow details and we’ll work through it with you.
Quick start:
- Don’t assume “deficiency” right away
- Look at what changed in the last 3–7 days
- Check pH, environment, and watering before adding nutrients
- Use the template below for faster, more accurate replies
Start Here — Use This Template
Copy/paste into your reply:
Grow setup: indoor/outdoor, tent size (if indoor)
Light: type + distance from canopy
Medium: soil / coco / hydro (brand if relevant)
Stage: seedling / veg / flower (week # if known)
Watering: frequency + runoff yes/no
Nutrients: brand + dosage
pH: input + runoff/res pH (if measured)
Temps & RH: day/night if possible
What changed recently (last 7 days):
Photos: full plant + close-up + underside
The more context you give, the easier it is to narrow things down.
Before You Assume It’s a Nutrient Deficiency
A lot of leaf problems get labeled “deficiency” too quickly. Start with these questions:
- Did watering frequency change?
- Did you increase nutrients or add a supplement?
- Did you lower your light or increase intensity?
- Did temperature or humidity shift?
- Is your pH actually measured and in range?
If something changed recently, that’s often the trigger. Plant stress can show up a few days later.
Before adding nutrients, rule out:
- pH imbalance or lockout
- Environmental stress (heat, light, airflow, humidity)
- Overwatering or poor root oxygen
Stacking fixes usually makes things worse.
Where Is the Problem Showing Up?
Location matters.
Lower / Older Leaves First
Often linked to:
- Mobile nutrient issues (like nitrogen)
- Root or watering problems
- Natural late-flower fade
New Growth / Top Leaves First
Often linked to:
- pH lockout
- Light or heat stress
- Immobile nutrient issues (like calcium)
Random Spots or Speckling
Consider:
- Pests
- Leaf spray damage
- Fungal issues
- Environmental swings
Visual comparison guides:
https://www.ilovegrowingmarijuana.com/growing/identify-marijuana-plant-problems/
https://www.ilovegrowingmarijuana.com/growing/leaf-problems-marijuana-plants/
Common Misdiagnoses
These come up constantly:
- Overwatering mistaken for nitrogen deficiency
- Light stress mistaken for magnesium deficiency
- pH lockout mistaken for multiple deficiencies
- Heat stress mistaken for nutrient burn
Before adjusting feed, confirm:
- Input + runoff/reservoir pH
- Temperature + humidity
- Light distance/intensity
- Watering rhythm
Quick Symptom Direction Guide
(Not a diagnosis — just general direction.)
- Burnt tips / crispy edges → often excess nutrients or environmental stress
- Very dark green + clawing down → commonly overfeeding
- Taco/canoe leaves → usually heat or too much light
- Whole plant drooping → watering rhythm or root oxygen issue
- Spots + underside activity → check for pests
Real Leaf Issue Case Studies From the Forum
If your symptoms look similar, these solved threads are worth reviewing.
Yellow Leaves
Watering + pH imbalance:
https://ilgmforum.com/t/help-yellow-leaves/118385
Normal vs abnormal yellowing:
https://ilgmforum.com/t/leaf-yellowing-normal/109554
Late-flower fade:
https://ilgmforum.com/t/when-is-yellowing-leaves-normal/50240
Curling & Burned Edges
Deficiency vs toxicity:
https://ilgmforum.com/t/deficiency-yellow-leaves-edges-curling-up/76470
Environmental stress case:
https://ilgmforum.com/t/new-leaf-issues/115272
Flowering Stage Leaf Changes
https://ilgmforum.com/t/leaf-change-problem/115552
Multiple Overlapping Issues
https://ilgmforum.com/t/help-identifying-multiple-issues-leaf-symptoms-photos-attached/103893
Symptom Reference Chart
https://ilgmforum.com/t/symptom-checker-link/42282
Frequently Asked Questions
Why are my cannabis leaves turning yellow in veg?
Often overwatering, pH imbalance, or nitrogen-related issues. Check pH and watering habits before increasing feed.
Are yellow leaves normal during flowering?
Some fade late in flower is normal. Rapid or uneven yellowing earlier usually means stress.
Can too much light cause leaf curling?
Yes. Excess light or heat can cause taco leaves or bleaching at the canopy.
What does nutrient burn look like?
Burnt tips that move inward if feeding remains too strong.
How do I know if it’s pH lockout?
If multiple deficiency-like symptoms appear at once and feeding hasn’t changed, check pH first.
Experienced Growers — Add Your Insight
If you’ve dealt with something similar, share:
- What it looked like
- What the real cause was
- What actually fixed it
Clear reasoning helps everyone learn.
Final Note
Leaf issues look worse than they usually are. Most are fixable once the real cause is identified.
Post your plant and details below — we’ll work through it with you.