I recently adopted a 8 month old yorkie and about 3 or 4 days ago a red spot, about the size of a half dollar, appeared on the middle of her back. I thought it might sunburn (though she doesn't spend more than 10 minutes outside at a time). But About 2 days ago the spot turned dark brown and got a rough texture. It doesn't appear to be bothering her, but it has me concerned. Does anyone know what this could be or what may have caused it?