Unknown user deleting files from different IPs

Hello,
Recently a number of entries were made in the Audit Log with the following pattern:
Description
deleted WPHB Minify Group "34970c23330f783c770f6daea8099319-scripts"

Context Type IP address User Date / Time
WPHB Minify Group Content 78.46.79.137 Guest December 9, 2017 3:24 am

There are a lot of entries like this and there is no user associated with the entry. Many of the entries have different user IP but there are some clusters.

Thanks kindly,