No - group submission settings are deliberately locked once students have submitted work, because changing the settings at that point would result in a horrible mess. The best-case scenario would involve all the different individual submissions from members of the same group being somehow merged together, worst-case scenario would be the existing individual submissions simply becoming completely inaccessible in the interface. Neither of those sound like nice features to have ...
If submissions have already been received, I suggest you create a new assignment with the correct settings and contact all your students to ask them to submit their work to the new assignment.
If submissions have already been received, I suggest you create a new assignment with the correct settings and contact all your students to ask them to submit their work to the new assignment.