Have you checked cleanness of the headphones? Sometimes ear wax gets inside the silicon buds.
Ear wax is not dirty, it's natural for ears to have a little. It's cleaning fluid for the ears, and as you get your head wet in shower, it comes out n removes dirt. Ear wax only bad if it's blocked n causing hearing issues. Sometimes in very hot weather you produce a little extra, and it gets on buds esp as they inside.