PMP Practice: Appraise team member performance against key performance indicators

Oluwaseun Adebayo-Ige is leading an agile software development team at Sourdough Signal Corp building a machine learning platform. During sprint 8 of 12, the product owner expresses concern that while the team consistently completes their sprint commitments, the velocity has remained flat at 34 story points for five consecutive sprints despite early projections suggesting it should reach 45-50 by now. The product owner asks Oluwaseun to implement individual performance metrics tied to story point completion to identify underperformers and 'motivate the team to increase output.' Team morale is currently strong, and retrospectives show the team values their collaborative culture. The technical lead privately mentions that the team has been deliberately taking on more complex, technically challenging stories that require more pair programming and knowledge sharing, which they believe is building long-term capability. What should Oluwaseun do?