YOUR BAKING SODA AND/OR BAKING POWDER HAS EXPIRED
Leavening agents are key to a fluffy, light cupcake. If your leaving agents are expired, your cupcakes will likely sink in the middle.
YOUR OVEN TEMPERATURE IS TOO HIGH
Oven temperature is vital to a properly baked cupcake. If your oven temperature is too high, your cupcakes will rise too quickly. Then, this will cause them to fall flat as they