I could have sworn one of my BP's had a white throat just like the rest of her underbelly. Last week I noticed the dark coloration. I thought she had gotten dirty, so I gave her a bath. It didn't wash off, so I thought maybe she had always been dark there or maybe she had turned dark there. Yesterday I noticed her soaking that area in her water dish. I thought that was a bad sign, so I got a wet paper towel and rubbed the area. Nothing came off. Do you think this is this something to worry about?