Hello P....
I didn't have the time to read all of the requests, so I apologize if I am repeating...but, here is what I recommend from my experience...
First... you can check out a great product at www.smellytowel.com
OTHERWISE...
Here is what I recommend:
If you are using a new fangled, high efficiency front loading washer, like I am, I have learned (now being on my second one) that they are notorious for harboring mildew--which can transfer onto the items you are washing. So, if you do have one of these machines, you might want to open the door and give it a good sniff--if the washer itself smells musty, then you might want to start by cleaning it first by spraying the gasket with a solution of oxy powder (it will tell you how to dilute it right on the tub and you definitely want a heavy solution)...allow it to sit for 10-15 minutes before wiping. Then, run the washer on the sanitary cycle (having dumped a fully rounded scoop of the Oxy Powder into the machine itself---because I've also learned from experience that putting it into the dispenser can sometimes cause it to clog) and then pour plain white vinegar, yes, into the fabric softener dispenser, and run your cycle.
When the cycle is done, wipe the gasket down well and leave the door open in order to allow the machine to air out--overnight if possible. These steps should remove any existing mildew. If it's really bad...you may have to do this twice.
HOWEVER...
If your washer is not adding to the problem, then here is what I recommend for the towels themselves: And, please note that I only recommend doing this to your everyday towels that you wouldn't mind possibly fading...as they may do so in order to truly sanitize them...
First, place towels into your washer and allow them to soak in a tub of hot water with 1/4 cup of baking soda...run a rinse cycle and then run another cycle and wash them in VERY hot water with 1/2 cup baking soda (1/4 cup for just a few towels), 1/4 cup borax (or 1/3 for a few) and add vinegar (about 1/4 cup for small-mid load, 1/2 cup for larger) to the rinse cycle. If possible, you may want to observe the rinse water for any sudsing. If you observe any soapy bubbles in the rinse water, you may need to repeat the first step...it may take a few rinses due to the fact that the towel fibers are releasing all of the residue. If there is no residue, then dry them immediately and thoroughly.
Just so you know...liquid fabric softeners can build up on towels making them less absorbent. I learned early on that most labels tell you to use much more than you need, so you might even want to try backing off on the amounts of detergent/fabric softener that you are using...it is not true that the more you use of them the cleaner/softer your clothing will be. Lots of things like mildew, smells and even dirt/grime will want to cling to your items from the residue that is left over. 1/4 to 1/2 cup of white vinegar in the rinse cycle will naturally soften towels and help retard mildew growth. I use Borax in place of fabric softeners, and I always use baking soda along with my detergent--and I also cut back on the amount it says to use in order to eliminate any residue. Note: Use only a white vinegar...not balsamic or cider.
I sure hope this helps!! ~Kimberly