Hi James
Thank you for the screenshots . . .
So it is your Windows folder that is increasing in size, there is a 4GB increase since yesterday
To narrow this down further and to possibly find the cause of this, in TreeSize expand out the Windows Folder, and take a screenshot, then wait a couple of hours and do the same.
Then please post both screenshots and once I have worked out which sub-folder is increasing, we should know the cause of all this . . .