Perhaps tomato ringspot virus.
See the link -- (Once there, scroll down to the section headed fruit. Click the link for Tomato Spotted Wilt)

Here is a link that might be useful: tomato problems in Michigan

You might also contact your county's Extension Service office. Use the map at the link below-

Here is a link that might be useful: locate your County's Extension Service office

Thanks for the info, I'll look into it and see if I can find out what it is.

Please let us know if you find an answer.