I have a 5 month old female boxer. She still has some pink bare skin on her belly. Around her last two nipples (toward her rear end) I have noticed that the pigmentation of her skin is changing. It is kind of blotchy. It is changing to the color brown. Is this a normal change much like when the paws turn black, or do you think that this is something that I should go to the vet with. If anyone could help I would be very thankful. ryan