HI. My horse has a a beautiful long mane apart from a bit just above the withers. Where it is about 1.5 inches long for about 4 inches. Here is is thin and weedy looking. I thought it was her rug but it hasn't grown back now she is rugless. Does anyone know what this could be? It really spoils the look. I should say it is 1.5 to 2 feet long but it does gradient shorter to where its really short. So I guess that signifies she is rubbling it, I've looked for mites and can't see anything.