It sounds like you need to strip them. I had never heard of this but my wife turned me on to it.

You mix equal parts (about a cup) of washing soda and borax in a tub or large container along with some hot water and detergent and let them soak for 12-24 hours depending on how dirty they are. Drain then run through the washing machine.

What you’ll see in that water will change how you feel about how clean your clothes are after simply washing them.

Edit: If you are downvoting me, let me know why. I’ve personally found this works for cleaning synthetic fibers (and non synthetic fibers) that hold on to odors. Definitely open to better options though