Very long plotting time.

[KrisMie]

Hi. I am plotting on headless Ubuntu 20.04.2 Intel NUC NUC6CAYH (720RPM HDD, Intel® Celeron® Processor J3455 (2M Cache, up to 2.3 GHz), 8GB RAM) and I am experiencing long plotting time for k-32. I takes 3 days to complete one plotting. I have previously tried to plot on old Windows 10 PC with AMD Athlon 64 X2, 7200rpm, 8GB RAM and it took half the time.
Would this be normal for this set up?
I also noticed that currently htop reports 54h of plotting process time (for two queued plots) while i started it 6 days ago:

I am not sure how does process clock time management work but if the process is running 6 days, should it not be more like ~140h? Does 54h mean it's been actually only doing some work for 1/3rd of a time? Other chia processes also show 3-13h instead of about 7 days since started it. Is something wrong with my machine, Ubuntu config? Is it possible that chia processes are being paused or go to sleep randomly?
I manage my Chia from CLI and have remote GUI attached.
All suggestrions appreciated.

[KrisMie]

Update:
I have updated Chia and BIOS to newest version and as for now plotting time shortened to ~27 hours.