Grafana only shows what is stored in the database so for some reason you have gaps in your data. Can you double check that you are writing Rx data every 10 seconds. Maybe an error in your Telegraf config?
If you really think that it is Grafana that is showing the data incorrectly, then can you post the raw data that is shown in the network tab in the Chrome Developer Tools. Here’s a guide for that.
If you don’t care about the nulls in your data and just want to connect the lines, then there is an option for that in Grafana on the Display tab:
