This is a weird one: all my laundry comes out clean and smells good (using standard washing tabs + Comfort) except for polo shirts which smell of sweat. These are 100% cotton, as are most of my shirts, and the shirts smell great - whilst the polo shirts smell of old sweat. Undies, socks etc all smell good - the problem is just polo shirts. I normally wash at 40 degs and I've tried 60 degs which helps a bit but the smell is still there. I've tried 'super-wash' and also giving it an extra rinse. I've tried washing them on their own, with just 5 or 6 in the washer so they have plenty of movement - nothing seems to work. Anyone else had this? Is it something in the type of weave of the material perhaps? What else can I try?