Even if the members of a group are signed to different labels, there's a possibility they could still release something as a group. Look at Wu for instance, they have a deal as a group with one label, while each member is free to have their own solo deal with any label they want. It's just a matter of the artists wanting to do something as a group, and then the record labels playing nice. If Prozak were with Strange, and Mike had contractual obligations to Psy, then they could still release something as a group on either label (or have it be a joint venture release). I imagine Strange and Psychopathic have a pretty good working relationship, so I doubt it would be a problem. Now King Gordy's label however, has put their foot down in the past of him recording as a part of the group.
Though all that really only applies if Prozak were signed to Strange which is... whatever.