I am wondering if the rust may be caused, by the high humidities that we had this past summer. While working on a quilt,
you may want to spread it out, when you put it away in the evenings to work on it the next day. I know that here on the Eastern Shore of Maryland, things, this past summer, often felt damp, even with the a/c on. Maybe fresh circulating air is the answer. I am so sorry that you have this problem and am hoping that you can restore it.