The JM I got a few days ago is starting to develop gray spots on its bark. The bark was formerly smooth and reddish, as is expected of a young branch, but now has a spread of blemishes.
Is this the natural maturation of a tree, or should I intervene lest the money and plant be wasted? It seems abnormal given how rapidly it's happened.

That should be a graft, not a cutting. The forum and my phone aren't playing nicely enough for me to edit the post, apparently.

is it loose, when you rub it does it come off?

No, the spots are quite firmly attached.
If it's relevant, the buds are just starting to open up.