Stop Using Old Ingredients
A lot of shelf-stable ingredients go into baked goods. Baking powder, salt, and even flour have rather long shelf lives. That being said, they don’t last forever and old ingredients can really mess up your dish. Baking soda, for example, is an active ingredient, so it can go bad.
Not only will old or expired ingredients not work as well as they should, but some of them can also even become toxic. Check the dates on everything if you have not used them in a while and make a habit of tossing things every three months as a rule.