Just as a quick reminder, new Switch firmware updates often bring controller updates, too. With Switch's Version 10.0.0 firmware update now available to download, you'll find that your Joy-Con can also be updated.
After updating to Version 10.0.0. ourselves, we've noticed that all of our Joy-Con needed an update but our Pro Controllers were seemingly fine. Nintendo doesn't provide information on what changes are made to any controller updates, but it goes without saying that it's worth keeping them up to date to avoid any unnecessary issues later down the line.
If you need a bit of help, follow the steps below:
How To Update Your Nintendo Switch Joy-Con
1) Make sure the Joy-Con you wish to update are attached to the console.
2) From the Home menu, choose 'System Settings'. Then choose 'Controllers and Sensors' from the left-hand side.
3) Scroll down to 'Update Controllers', press it, and let the console do its thing. Make sure to repeat all steps for all of your Joy-Con.
Version 10.0.0 has brought a couple of new welcome features, including the option to change button mapping.