I've noticed "cracks" in the sidewall in the last couple sets of Hoosiers I've purchased, but they are not really cracks. Looking very closely you may see they're tiny ridges left over from the tire mould during production. If that's what you have don't worry about it. If you really have cracks and can see gaps, I'd take them back to the distributor or contact Hoosier directly to report it.
AJ