Thank you so much for all of your suggestions regarding the towels! After reading your comments and researching a little bit on my own, I cleaned my washing machine with white vinegar and a little bit of bleach (poured them into an empty, hot wash cycle), hoping to get rid of any residual build up. I also purchased some OxiClean and rewashed the stinky towels... I don't know if the smell is 100% gone, but it is already SO much better! I'm going to try washing them one more time. I have a feeling that the odor will be gone, never to return again. Praise the Lord! I really do hate smelly towels!
More later, but for now, I need to get ready for church!