The rubber backing on the rugs is the culprit. Because vinyl and rubber don't mix, it creates a reaction and causes the vinyl to actually turn yellow. Also, other things can react and cause stains.

We have small throw rugs with rubber backing on two bathroom linoleum floors, which have yellowed from the imprint of the rubber backing. We have tried every known cleaner without success.

The rubber backing on the rugs is the culprit. Because vinyl and rubber don't mix, it creates a reaction and causes the vinyl to turn yellow. Also, other things can react and cause stains.

Rubber-backed bathmats or rugs can leave a yellowish stain on vinyl flooring.

The rubber backing on some rugs reacts with vinyl to cause yellowing, and there’s not much you can do.