Hi @Paul Rinckhoff Yellowing leaves on a weed plant are a sign of stress, but the underlying cause depends on where the yellowing starts, how it appears, and the plant's growth stage. To diagnose the problem, examine whether the yellowing begins on older or newer leaves, whether it is uniform or between the veins, and whether the leaf tips or edges are affected. Common Causes & What They Mean Bottom leaves turning yellow - Often indicates a mobile nutrient deficiency (such as nitrogen or magnesium), overwatering, or natural aging. - During vegetative growth, this usually points to a problem that should be corrected. - During late flowering, yellowing lower fan leaves is often normal as the plant redirects nutrients to developing flowers. Top leaves turning yellow - Commonly associated with immobile nutrient deficiencies (such as iron), excessive light intensity, heat stress, or pH-related nutrient lockout. - Bleached leaves closest to the grow light often indicate light stress. Yellow tips or leaf edges - Frequently caused by nutrient burn from overfeeding or, in some cases, potassium deficiency. - Burnt tips while the rest of the leaf remains green typically suggest excess nutrients. Common Causes & Recommended Fixes 1. Watering Issues - Overwatering: Saturated soil limits oxygen at the roots, reducing nutrient uptake. Plants often appear droopy with pale or yellow leaves. - Underwatering: Leaves may curl, become dry or crispy, and eventually yellow or brown. Recommended fix: Water only when the growing medium has dried appropriately for your setup, and ensure containers have adequate drainage to prevent waterlogged roots. 2. Nutrient Deficiencies - Nitrogen deficiency: Yellowing begins on older, lower leaves and gradually progresses upward as the plant reallocates nitrogen to new growth. - Other deficiencies (such as magnesium, iron, or potassium) produce distinct yellowing patterns that depend on the nutrient involved.