I see this sometimes on older Sedum stems, but to me yours looks a little too symmetrical. Is the spotted areas firm?

Yes they are.

It's nothing. Last nite I wanted to show you a pic, but it was dark out. Here's a pic of one of my Sedum Adolphiis. You can see the stem is turning into bark. Mine was green at one time. Keep your eye on it, but tbh I don't think you have to worry. Your plant is just starting to age:).If you don't like the look, you could always turn your plant into a cutting. That's totally up to your esthetic:).

Great, thank you! I think I'll just let it be for now.