Grafana - add plug state to download/upload speed graph

I have a broadband speed graph in Grafana that shows the download and upload speeds in Mbits/s.

I also have a process that does a speedtest every 10 minutes and, as a result of some issues with current speeds on my router slowing down after a period of time, the zigbee plug for my router is stopped and then started again to reboot the router id the speeds have slowed to an unusable download rate. So for a few seconds, the plug switch is in a state of “off”.

It would be great if I could slot in a bar into this graph that would show that period, thus allowing me to see when the reboot occurred and how that affected speeds. Can this be done? And if so, how?