Seems that the charts on the admin performance page within the dev dashboard are currently broken/not appearing. The value for each web vital still shows though.
Other people have reported the same issue too.
Hey @Luke 
- we pushed a fix for some similar issues in the Dev Dashboard yesterday, can you let me know if you’re still seeing this? If so, I can prioritize on my end here!
They have reappeared now, so all good here Alan, thanks!
Glad to hear it’s working now - let me know if you see this pop up again though @Luke