Hi I have 3 girls, we have an Elsa dress the cape is yellowing on. I have tried to be gentle whitening it, but now I need more help. So has anyone needed to do this? Or do you have a whitening tip for gentle clothing you love? I should mention the rubbery texture of the snowflakes could be making it hard to whiten. I don't need them bright white again, just enough to not look yellow.