A falling alocasia leaf is alarming when the plant has only a few leaves to begin with. Before changing every part of its care, check whether this is one ageing leaf or a continuing decline.
Look at new growth, the remaining leaf surfaces and the bases of the stems. Inspect for pests and check the growing medium below the surface.
Trace recent changes
A move, cooler conditions, weaker light or a pot that stays wet can all belong in the investigation. Record what changed and when, rather than assuming that leaf loss always means the same thing.
Do not respond to a small number of leaves by feeding heavily. Nutrients do not replace suitable root conditions or light. Equally, avoid deliberately drying the plant without checking its actual needs.
Keep dated photographs of new and old growth in similar light. A damaged leaf may still be lost after a growing problem has been corrected. The more useful signs are whether damage continues, whether tissue remains sound and whether later growth develops appropriately. If the problem progresses, seek advice using the plant's identity and that history.
NC Extension’s Alocasia profile lists excessive water, insufficient water and inadequate light among possible reasons for yellow leaves. Leaf loss alone therefore does not determine which part of the routine needs changing.
Related reading: Black-Leaf Alocasia Care: Light, Watering and Humidity.