I just noticed the same thing. I got a notice from Comcast that I was over my data limit this month. Looking through my router logs (Unifi Dream Machine Pro) my pi-hole averaged 5-30 MB of data usage a day until December when it jumped up to 80GB per day being uploaded. I'm going to try taking it offline tonight and see what happens. Any other things I should check and troubleshoot?
Here are the results from my query:
echo ">stats >quit" | nc localhost 4711 domains_being_blocked 1075391 dns_queries_today 190210 ads_blocked_today 3299 ads_percentage_today 1.734399 unique_domains 25448 queries_forwarded 181851 queries_cached 5049 clients_ever_seen 33 unique_clients 21 dns_queries_all_types 190210 reply_NODATA 784 reply_NXDOMAIN 538 reply_CNAME 12487 reply_IP 22784 privacy_level 0 status enabled
Looking forward to learning what's going on here, thank you!