Linux Fedora suddenly much slower... only on one computer

I have two computers running fully updated Fedora 40. The two computers have the exact same packages installed. They are not identical, but very similar and bought at the same time: Dell Optiplex 7000 (SSF vs Micro). They have always performed essentially identically. Yet, this week one of the two began to behave *MUCH* slower than the other. Around 1/3 the speed. Commands top, free, and the benchmarks for the NVME SSD's show no sign of problems. It does not seem to be any process slowing down the computer. The one that has problems is the Micro, that has 16GB of DDR5 RAM vs 24GB of DDR4 of the SFF. I tried working in different NVMEs, I tried switching to an older kernel (kernel-6.10.11 vs kernel-6.11.3)... Nothing... Any ideas?