By isolate the dye I mean using either an acid to neutralize the pH of the dye, using an anti dye to prevent redposition of the dyes or using a dye set to stop the bleeding. Either way, if a rug makes it the wash floor and starts bleeding, or we expect it to bleed, we will continue rinsing to remove majority of the fugitive dye as we are correcting it. Often simply bringing the rug to the acid side is enough to stop the bleeding.
But with what you described, I'd like to know if you are talking about cotton face fiber tufted rugs or tufted wool rugs with cotton backings? There is a bit of a difference there. And you say you are using masterblend products? Which ones specifically and are you using a rinse to neutralize any alkaline residue?
And why are you full washing the tufted rugs? Do they have urine issues or severe contamination that nessessitate a full wash? If not you may be better off dusting and surface cleaning these rugs, as they often will have either poorly dyed wool, accents such as silk or rayon (art silk/viscose etc.) that will bleed easily as well. Add to that, the science behind the centrifuge requires that the water migrates through the layers of the rug and out the cylinder.. the latex in the tufted rugs already present a barrier to this and we find they often need to be spun twice in order to maximize the moisture removal. Adding a contact barrier may be further hinding the water migrations and causing and dye that might migrate out to settle in the pile.
Just some things to think about.