Diagnosis
Diagnose: ZZ Plant Yellow Leaves
Use these observations to decide what to check next.
Assess the pot and the changing leaves together
A gradually yellowing older leaflet on an otherwise stable plant can reflect aging. Several changing leaves, a collapsing base, or progressive wilting need a broader check.
Wet mix is a reason to investigate aeration and drainage, not proof of rot. A very dry root ball supports drought, but neither leaf color nor rhizome firmness alone establishes the condition of the whole plant.