You didn't mention your welding process but it is likely that 403.5 applies as a supplimental essential variable.
See the explanation of supplimental essential variables and how they apply to notch toughness testing requirements. If you do not have to comply to any notch toughness testing requirements per your manufacturing code, then the current PQR (P-1 Group 1 to P1 Group 1) will support your WPS for welding the P-1 group 1 to the P-1 group 2 material.
The change is not an essential variable concern for welder qualification work.