Hi huhhah
This could be a low RAM issue. Large pages using most of the resources. Try adding additional RAM to Whonix-Workstation with rads. You can also terminate any unneeded processes on the host to free up RAM if needed.
https://whonix.org/wiki/RAM_Adjusted_Desktop_Starter
This could also be related to Tor Browser E10/multiprocess which can affect performance.
https://forums.whonix.org/t/research-disabling-tbb-e10-mutiprocess-for-performance-boost/6431