This happened at some point in the last 24 hours.
Some of the affected dashboards and panels I've spotted (I'm sure that there are many more):
https://grafana.wikimedia.org/d/000000551/performance-perception-survey?orgId=1
https://grafana.wikimedia.org/d/000000249/edit-stash?orgId=1
https://grafana-rw.wikimedia.org/d/000000208/edit-count?orgId=1&refresh=5m
https://grafana.wikimedia.org/d/000000085/save-timing?viewPanel=11&orgId=1
https://grafana.wikimedia.org/d/000000143/navigation-timing?viewPanel=12&orgId=1
https://grafana.wikimedia.org/d/000000002/api-backend-summary?orgId=1&refresh=5m
When you edit any of these panels that states "no data", you find that the queries have been emptied (or can't load, who knows):
The history shows that they haven't been touched recently: