I have a bunch of those artificial Christmas trees that used to be the prettiest, brightest white color.....But now, well they're this dingy yellow, brown pukey color . Does anyone know of an easy way to spruce these up again??? I was hoping to use them in some parades this December, so I've gotta get to work if I'm going to use them. All of your suggestions will be appreciated.... Remember December is practically knocking on the door, so I need fast methods of cleaning them up! Thanks in advance!