Alas for the MU, NU, KU, TU and JS series where the diffuser gets cooked. The diffuser is directional, allowing more light to reach the top and less at the bottom.
If you rotate the sheet (Do not flip the sheet over) so the burn marks are at the top, it will result in a picture that's OK at the bottom but gets gradually darker towards the top.
One solution I read about seems productive but not necessarily profitable. It involved using a dremmel to clean up the burn marks, but when fitting new LED strips, move them 1 to 1.5 cm sideways, so that each LED ends up between the burns. This requires some cutting off to the extreme end stop for the strip, as well as the recess for the LED connector.
The last one I did was without modification. Ended up with fair to middling result, so it was a take it of leave it situation. Bruce