You manage a fine-tuned GPT model deployed in Azure AI Foundry that summarizes legal contracts. Two months after deployment, users report that summaries have become less accurate, though no code or model changes were made. You suspect the input distribution has shifted as newer contract types are now being submitted. You need to confirm whether the fine-tuned model's output quality has degraded on the newer inputs before deciding to re-fine-tune. What should you do FIRST?