I have a problem cleaning my dress shirts. I don't send them to the dry cleaners but just wash them alongside my other laundry. However, I find that the color (especially my blue shirts) fades around the collar area (starting from where the button is and gradually moving up where the fold of the collar is). I'm very frustrated about this because the shirts are all expensive.
The problem is not your detergent but rather your natural body oils and sweat as well as the naturally occuring chafing from your neck. The only solution I have found for my husband is to get his shirts with collars that are just slightly bigger than normal for him so that the collar itself doesn't "ride" right on his neck.
I believe the discoloration you describe along the collar fold happens to all shirts over time and is an unavoidable . You may need to break down and replace the shirt. You can find great buys on even designer stuff, 100% cotton, in the thrift and consignment shops. (Although men's stuff in thrift shops is generally more worn and stained than women's.) On the faded polo shirts, you might try dyeing them, if you can find a good color- and if that doesn't work out, again, check out the thrift and consignment shops.
Make sure you give the detergent time to dissolve in the water before putting ANY clothing into the washer. That should take care of the random spots on your polo shirts.I would also recommend washing all your clothing in cold water to prevent fading.
You might be a Psychokinetic. My clothes get faded at all the shakra points and my hands I think. It has to do with your energy flow just think of a different color when your sweat rage seems to fade the clothes and clam blue thoughts seem to stop it from happening.