Lock Columns After Update Request Submitted

I have contacts (who do not have access to the sheet) submitting information via update requests (URs).

Once they do this, we type a response in a column that triggers another UR for them to fill out another field of information. These second URs include their responses from the first one so they can see what they wrote and what our whole correspondence was.

But this can be confusing because in the second UR it looks like we are asking them to fill out the previous fields again when we really just want to show them what they entered the first time.

Is there a way to set it so that once they submit their first UR, it locks those columns and they become view-only? This would be row-specific, obviously, to only the rows where the initial URs were submitted.