Well, if the container you bought has a smell to it, that smell can be transferred to the buds. Some plastics, especially newly-made ones, may still be in part of their curing process, releasing small amounts of gasses into the air. Some plastics are better than others. Some are even chemical-grade and used in laboratories. Smell the containers you have to choose from and avoid those that have any smell. They should be washed well before using, and that can get rid of some lingering factory smell. Mild heat can also encourage gasses trapped in the plastic to escape.