I would first contact the Michigan DNR headquarters and be directed to their permit office. Explain that your turtles were purchased legally outside the state and the situation. They should be able to lead you in some direction. They may also direct you towards a USDA permit as well. Spotted's are listed as State Threatened in Michigan and are protected under Michigan's Endangered Species Act so you may have to prepare for an extensive process before you can sell those offspring so as you do not violate the Lacey Act or Mich. state laws. Good luck and let us know what they have to say, it might help others in the same situation know the process.

-JG