Horrible performance, super slow

I'm running 2024 on an intel imac with 64 gb of ram (3.6 GHz 8-Core Intel Core i9). I have this strange situation where playback is okay at the beginning of the work day, but by the afternoon, it goes to almost zero. Terrible response time on edits. I've tried all the typical tricks like clearing caches, dividing up the project, and changing prefs. No luck.