My mare's mane/tail is multi-colored. One of the predominant colors of her tail is white. The middle to the ends is not as white as it should be...which is blinding white as it is at the top. I have washed it w cowboy magic and heavily diluted liquid tide. It helped, but it didn't completely remove all "dirt stain". Anybody know of a good product that won't also lighten the other colors on her tail?