Since we are in the 14th or so week of 2017 and this only goes through the 12th week, I'm assuming the drop at week 12 represents an incomplete week? In other words the statistic snapshot was taken early in the week?
I think such a drop in the total Xweb activity could be completely explained by just one thing; "papa Tony" hasn't been here as much as usual.
I've been away for some time myself...how you doing Tony? Hope all is well with you.