GPU Rendering Slowdown

I'm rendering a whole bunch of clips to h.265 from a timeline. Sources are mostly ProRes but some are MP4. When I started the batch (about 30 clips, each about 10 minutes long), it was running quickly. Now near the end it's running at just about, if not slower than realtime.  Looking at task manager, the nVidia RTX5080 is running at 5%, the Intel GPU at 8%, and processor at 24%. This is much slower than normal.

I know it's not drive speed because it's a NVMe array capable of over 1GB/s, and it's logging 1% write

What gives?
 
System info
    Application: Adobe Media Encoder (Beta) v25.6.0.62
    OS: Windows v10.0.26100, RAM: 63.79 GB GB, CPUs (logical): 16