Why Are My Leaves Turning Yellow in DWC or RDWC?

Why

Yellowing is chlorosis: too little chlorophyll. Browning usually means damaged or dead tissue. One problem can cause both.

For yellowing leaves, ask three questions: Which leaves? What pattern? What changed?

One or two oldest leaves fading while the rest stays healthy may be normal aging. Monitor them. Spreading yellowing needs investigation.

Across many plants, broadly yellow older leaves can suggest nitrogen shortage. Yellowing between green veins on older leaves can suggest the plant isn't getting enough magnesium. On new leaves, the same pattern can suggest it isn't getting enough iron. These are clues, not diagnoses. Leaves are pretty good witnesses, but terrible lab reports.

Did this follow a reservoir change, top-off, additive, or lighting change? In RDWC, compare affected and healthy plants sharing the solution for clues to shared or local problems.

Before adding nutrients, inspect the roots. Slime, mushy tissue, or bad smells need investigation. Color alone doesn't diagnose rot. Check aeration, circulation, and water temperature at the affected plant. Repair failed airflow or blocked flow, and correct unsuitable temperature. Suspected root disease needs diagnosis.

Check pH and EC with calibrated meters against your crop's targets and recent readings. Wrong pH can restrict nutrient availability. EC measures overall salt concentration, not nutrient balance. Too weak can mean shortages; too strong can stress roots. Normal EC doesn't rule out a missing nutrient.

Compare every component and amount with your complete nutrient recipe and actual water volume. Correct confirmed shortages using the recipe. Dilute excessive concentration with suitable water. Replace an unknown or unbalanced mix with a correctly mixed batch. Let it circulate, recheck EC, then adjust and recheck pH for your crop.

Also inspect leaf undersides for pests, especially with speckling or webbing. If damage follows the strongest light exposure, check intensity and distance. Confirm the pest or excessive light before treating or adjusting. Still unclear? A plant diagnostic service can help select the right tests.

Compare photos under the same light. Look for yellowing to stop spreading and healthy new growth, not overnight recovery. Damaged leaves may stay damaged. Read the pattern. Verify the cause. Make the correction.

Related Grow Pops answers: https://www.growpops.com/grow-answers/why-are-my-leaf-tips-turning-brown-in-dwc-or-rdwc and https://www.growpops.com/grow-answers/why-are-my-leaves-curling-in-dwc-or-rdwc