Yellow leaves are a symptom rather than a single diagnosis. Start by noting whether yellowing begins on old or new growth and whether it affects the whole plant or only one area.
Checks to make first
- Measure reservoir pH and electrical conductivity with calibrated meters.
- Inspect roots for browning, slime, damage, or poor aeration.
- Confirm the nutrient mix and dilution rate match the crop and growth stage.
- Check water and air temperatures, light intensity, and recent changes to the system.
Recovery
Correct one confirmed cause at a time, replace badly imbalanced solution when necessary, and watch healthy new growth rather than expecting damaged leaves to turn green again.