Sudden Leaf Drop
A plant dropping several leaves at once is almost always reacting to a change in its environment.
Common causes
Relocation shock
New light, temperature, or humidity after a move (or coming home from the shop) can trigger a drop. Give it a couple of weeks to settle before intervening.
Draughts and temperature swings
Cold air from doors, windows, or air-conditioning can cause leaves to fall. Move it to a more stable spot.
Watering extremes
Both severe drought and waterlogging cause leaf drop. Check the soil and correct the routine toward a steady middle.