Unbleached prefold diapers are not whitened and not bleached. Thus, you can often see the little brown and black flecks that are normally present in cotton. These specks are normal. Some of it will wash out in the initial prep washes and some of it will not. It's fine. You don't typically see them in cotton because cotton is normally bleached, whitened or otherwise pretreated so that these flecks are not visible. No worries. They are normal and are first quality. If the flecking bothers you, choose whitened diapers.
Flecking amount will vary and it will get much lighter over time with more washing. The little hanging thread in the corner of the picture on the baby should be trimmed with scissors. Some corner frays and hanging corner threads are normal and should be trimmed with scissors. If a fray goes past the vertical edge stitch, that is a defect. Please use the Contact Us link of that happens.