It is so sad to find dye running in pre-cuts, but it is better to find out about it now rather than after they are sewn.
I would recommend filling a sink with hot water and dipping the strips of the same fabric into it. You can pre-test by dabbing damp white fabric on a sample, but I like to get them completely wet. If the water turns color, then add little Retayne and proceed with very hot water, soaking for 20 minutes (as stated on the label), and gently mixing so that the water flows through the fabric. I don't stand there and mix for 20 minutes, but I come back every few minutes and mix some more. When finished, rinse in cold water and see if there is any more bleeding.
Others have stated on the forum that although vinegar was used to "set" dyes years ago, it is ineffective with the modern dying methods.
Best wishes!
Dayle