Hi Nick,
I was looking at it before but unfortunately had to move onto some other work.
I looked for the 15th when you last had an issue and I noticed one of your sites receives move visits than other days. However, I didn't have time this morning to confirm that with other dates in the logs.
I also noted you get quite a few brute force attempts on SSH. You should consider changing the SSH port.
In regards to what has changed, potentially many things. cPanel changes often and the resource amounts used can change along with it. There is also the possibility we turned off burstable RAM on that node at some point (I'll look into this).
Kind Regards,
John - Managing Director