@IM35461, Can you do a
ls -lah /var/log
and post the output please?
Any rotated files (with a .X where X is a number) can be deleted.
If you use this command -
sudo truncate -s 0 /var/log/[the log file name]
on the largest files listed, you should find the data inputs restart.
I have outlined a process here to change the way the logging happens and then how to manage the log files. If you want to have a go at this the please start a new thread. It would be useful as it would add evidence to my theory.