Hello, let's see if somebody might know the answer to this mystery. A few months ago, I noticed a dark stain appear on the outer edge of the nail that's next to the pinky. It runs from bottom to top of the nail and when I look at the edge of the nail, the discoloration seems to be embedded IN the nail, in other words, it doesn't stop where the nail is joined with the skin, but continues all the way to the tip of the nail. I thought at first that I hadn't taken off the nail polish properly and that dirt had accumulated, but after cleaning it thoroughly, saw that wasn't the case. Then I thought that it could be that I had worn shoes a litthe too tight, but the problem continues and the nail at the bottom is growin darker than the rest of the nail even though I haven't worn those shoes anymore. Now, I see the same problem in exactly the same place on the other toe (at the outer edge of the nail) but this isde is actually darker. Also the pinky of this foot seems to have the dark line running from bottom to top. I run 5 times a week, and my husnabd thinks it's trauma to the nail (judging by the location of all the stains) , but I'm worried it might be fungus. What do you think? Thank you very much.