The edges of the cuffs on a white, pique French cuff shirt that I have, close to the bottom (near the links) developed a black discoloration after the last time I wore the shirt. I assume the discoloration is from oils on my hands when tugging on the cuffs to extend the sleeves; because the sleeves are slightly short, I tug frequently so that they are at their maximum length. I have washed it twice now (cold water, no fabric softener), but the discolorations do not seem to be fading. Any advice on how to wash this? I am sure OxiClean would work, is that acceptable to use? Thanks.