I’m guessing this has been asked a thousand times, but how to remove or at least fade yellow sweat stains from armpits on white tee shirts. We’ve tried pretty much all the branded stain removers, bicarbonate of soda/baking powder mixed with white vinegar, bleach solution, oxy whitening powder stuff etc etc, but to no avail. My son has a million white tee shirts that were all quite pricey and are otherwise in great nick, but he won’t wear them with these stains on.. help me!!