I don't know the answer - sorry. I think it could have been the markers that your color catchers caught. Personally, I have never used color catchers when I wash a finished quilt because I usually prewash everything. IMHO, the washers do wash out. I will admit that there have been a time or two that I had to wash a second time to get them all out. I feel like when you can't see them anymore they are out.