Shrimp suddenly has black patches on tail?

[ArtsyAxolotl]

I just looked into my tank and noticed one of my smaller peppermint shrimp has three black patches on the top of hi tail. They seem very much on the surface, almost like scabs on a person or burn marks on wood or plastic. They weren't there here's several hours ago when I was fixing something that got knocked over (I have a hermit who loves my purple gorgonian despite it being far to weak to hold him.)

Any ideas? I tried googling it but all the black spots I see on shrimp are internal and in the body cavity, not on the tail. Is it dangerous to the other animals in my tank?

 

[ArtsyAxolotl]

I just realized the photo I attached was really crappy. So I took another. And I can't seem to edit the original post.