Talent Review meeting update few employee details when its already completed?

Summary

Talent Review meeting update few employee details when its already completed?

Content

Hello,

In Talent , we have a 'Talent Review' that was already completed - in status Completed.
However, we missed filling up the performance details of few employees and would like to update them. 
When trying to go to My client groups - Talent Review  - choose the review - > click on 'Conduct meeting' - we cant add the employees talent , without damaging all others employees details.

How can we update few employee's details when the talent review meeting is already completed ?

please see attached file.

Thanks a lot