Certain types of fabric like polyester (which we all tend to wear often during workouts) as we know actually encourages the growth/breeding of bacteria under the arms which is what creates unpleasant excess underarm odor.
I beleive that such fabrics also get worse in this respect as they age. I've had poly clothing that was mildly smelly after wearing, and then as the item got older it got smelly faster and more strongly. Also perhaps you are now using an eco-friendly detergent that is not quite eliminating the smell all the way when washing?
Try some new non-poly clothing items and see if that helps.

I also recommend the 'crystal' deodorant- it consists of mineral salts that prevent the underarm bacteria from breeding throughout the day- basically they don't like the salty environment. Worth a try as well.