Use the "Macro" feature on your camera, that will make close up shots focused!!! Cuz the pic you put up sucks ass, way too blurry to be able to tell you anything.
I wouldnt worry....It looks like only one leaf. Could just be a isolated problem. Sometimes if I dont rotate my plants, the leaves near a fan or the A/C get a different look
You need to add all the specifcs of your grow what soil? fertilizers ? etc. then after that you can go to the grow faqs and there is an analysis of problems with pictures to help you. But if you want my help you need all info and I will try?? If you feed with fertilizers sometimes if you get the water on your leaves they will turn a little yellow and spotty like that ??