→First determine WHERE the symptom sits (old/young, whole plant/shoot) and whether several patterns occur at the same time – that narrows down the cause faster than color alone.
→With interveinal chlorosis on lower leaves, first bring the root zone pH into the Mg window (coco/hydro 5.8–6.2, soil 6.2–6.8), then apply MgSO4 1–2 g/L.
→Uniform yellowing of old leaves in vegetative stage/early flowering = add more nutrients (EC +0.2–0.4); in late flowering it is fade — then do NOT counteract.
→Spotted, crippled YOUNG shoots with RO/soft water mean: dose Cal-Mag to 120–180 mg/L Ca, correct pH, and don't run VPD too low.
→Burnt edges on old leaves with a green center = K deficiency; first distinguish it from nutrient burn via EC, then feed with a K-emphasis and don't overdose Ca/Mg.
→Neon-yellow young leaves with green veins are almost always pH-related — lower root-zone pH (coco/hydro 5.8–6.2), choose the chelate to match the pH (EDDHA at high pH).
→Stippling on top + webbing underneath = spider mites; set the climate cooler/more humid, introduce predatory mites early, rotate active ingredients, never spray during late flowering.
→Silvery streaks + black fecal spots = thrips; use blue traps for monitoring and beneficial insects for leaf AND substrate — never forget the soil pupal stage.
→A single wilted leaflet in the bud is the bud rot early warning sign; keep late-flowering RH at 40–50%, keep air moving, remove infested buds in isolation — no cure.
→White, wipeable coating on leaf tops = powdery mildew; lower RH, move air, thin out the canopy and maintain strict quarantine — do not spray buds close to harvest.
→Wilting DESPITE wet substrate + brown, slimy roots = Pythium; stop watering, cool the solution (< 20 °C) and aerate it, clean the system, introduce beneficial insects.
→Dark green, claw-shaped leaves (The Claw) on YOUNG shoots = N toxicity; flush with pH-correct water, lower EC, and cut back nitrogen during flowering.