Iron deficiency

The newest leaves go pale yellow with green veins. It's almost always pH too high, not a lack of iron.

Symptoms

• Newest leaves turn pale yellow while the veins stay green.
• Older leaves stay normal.
• Severe cases: new growth almost white.

Quick checks

• Calibrate your pH pen, then re-test feed and run-off.
• Are the newest leaves affected (iron) or the oldest (magnesium)?
• Lift test for over-watering.

How to fix it

1. 1
   Check

   Calibrate and correct pH

   Calibrate your pH pen, then bring feed pH into 5.5–6.5, adjusting after all nutrients are added. Hydro and coco growers usually sit in the lower half of the window.

2. 2
   Environment

   Avoid over-watering

   Let the medium dry back properly between waterings.

3. 3
   Monitor

   Judge by new growth

   Give it 3–5 days.

Likely causes

• pH above 6.5 (common with hard UK tap water).
• A drifting or uncalibrated pH pen.
• Over-watering or cold roots.

What to avoid

• Don't add iron supplements before fixing pH.
• Don't trust an uncalibrated meter.

Prevention

• Calibrate the pH pen at least monthly.
• Measure your tap water so you know how hard it is.

When to get help

If new growth stays pale with a calibrated meter and correct pH, email info@monkeynutrients.co.uk with your readings and water type.

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