That was probably me, Lee. White vinegar. It should help on these stretchy fabrics, which are probably colored with acid dyes. It won't help with cotton dyes.
Places like Joanne's or a quilting supplier sell products specifically made for setting dyes. Amazon sells some too. Retayne, Raycafix, Dharma Dye Fixative, Aljo Pro-fix PCD are some of the products. Synthrapol is a wash for removing excess dye, and there's also a Synthrapol product for setting what's left, but this may result in a lighter looking color. I haven't used any of these products myself yet. Most carry warnings that are only important for 1:1 use, where there will be further laundering. Since this is probably a one-time washing we're talking about, any of them should help here.