Nitrogen deficiency
What to look for: Older/lower leaves pale first, overall weak growth, thin stems, slow recovery.
Organic response:
- Top-dress with finished compost or worm castings.
- Use diluted fish emulsion or alfalfa meal during active growth.
- Add grass-clipping mulch outdoors when appropriate.
- Avoid waterlogged soil because roots cannot feed properly.
Watch-out: Do not keep adding nitrogen if the plant is in low light, dormant, or already lush and floppy.
Image/source reference 路 Wikimedia Commons / nitrogen-deficient cabbage image