did you originally wash the fabric with some kind of color catcher? i use retayne. but others here have used household color catchers or color grabbers. even after quilting, i have used retayne where i thought/knew there would be a problem. i just wouldn't wash it without first sandwiching. can you baste thoroughly to a sheet, with either pins or thread, and then zig-zag the edges? the back side needs to be well-protected.
washing gently in cool or tepid water was good advice, too.