concern & question

Hi everyone. I usually follow along with the posts silently but this time I have a question. We have 2 DBT’s, approximately 7-8 years old. They have both always been very healthy. Over the last few months one has developed a redness on the trim of his mouth, upper and lower. The redness goes into his mouth some. He does not appear to be bothered or in pain. It does not seem to bother him when he is eating. I have attahced some pictures. He of course would not open his mouth for the camera but I hope I caught enough so you can see what I mean. I appreciate your thoughts and suggestions in advance. Densie and Jon Crowe