Both Retayne and Synthrapol can be used on commercial dyed fabrics. The difference is that Retayne sets the color, so you need to use it before you combine the fabrics or it will set colors all over the place. Never use Retayne on a finished quilt. Synthrapol suspends the dye particles in the water so they won't settle on the fabric. It can be used on a finished quilt, or on fabrics before they are put in a quilt. In your case, since the fabrics in the top were not pre-washed, I would test the batik to see if it bleeds. Not all of them do. But be sure to wash the completed quilt with Synthrapol and/or color catchers until the water runs clear before giving it to a baby.