High Unexplained Data Usage

The last couple weeks we have been experiencing high unexplained data usage, both upload and download.  We are able to track this via our router portal online.  I occasionally cross reference with xfinity and they're usually pretty close on total usage.

Over the course of the last couple years we have been averaging about 4gbs upload and 20-40 gbs download per day.  The most recent readings the last few weeks have been 15+ gbs upload and 60+ gbs download per day.  This usage pushed over the 1.2 tbs cap/month.  We are using the same if not less usage based on our connected devices.   Last night (4.29.24) we turned off the router about 10pm.  Woke up at 6am turned the router on and went right to check the data usage online via our router portal. We burned 18+ gbs upload and 120+gbs download over the course of about 7 hours with the router turned off.  I was thinking it was a bad read by our router but checked xfinity and it had moved 100+ gbs in total overnight as well with the router turned off.  This does not make any sense to me and is almost impossible given, for example, a typical movie in HD burns about 4ish gbs over the course of 2 hours. All devices were off while we were sleeping and again the router was turned off.

Anyone else have recent large unexplained data usage spikes? Anyone have a reasonable guess on what is going on here?