Use this checklist when leaves are yellowing. The goal is to describe the yellowing pattern accurately before deciding whether the issue is nutrient, root-zone, pest, disease, age, or environment related.
Final visual should compare uniform yellowing, interveinal chlorosis, marginal yellowing, old-growth-first yellowing, and new-growth-first yellowing at the same scale.
I am using the Chlorosis Pattern Checklist. Yellowing begins on [old/new] growth and looks [uniform/interveinal/marginal/patchy]. Current pH is [x], EC is [x], substrate moisture is [x], and recent changes were [x]. Help narrow likely chlorosis causes and what to verify first.