I wish I had an explanation or solution for you, but I don't. However, m any years ago, I made and sold my first consignment quilt, in a roman stripe pattern, using cotton fabrics in solids, plus black. Imagine my surprise and chagrin when the person who bought the quilt, called me and said that little holes had appeared in some of the black triangles. I was horrified, as it was the first quilt I had sold, ever, but I took it back, found that about half the triangles had little "holes" in them, but not all. I had purchased all new fabrics, but unless I accidentally switched out one of the black fabrics, I'm not sure. In any event, after much deliberation, I hand appliqued new black triangles on the quilt, then quilted over them, and thankfully, I did not hear about any more holes in the fabric. As careful as I try to be about buying my fabrics, this was a first for me.