All power off is a feature unique to the Lumos Firefly. You have the option of turning off one Firefly or having other of your Firefly lights turn off auto-magically.
By default, this feature should be enabled and will work once the lights have been paired with the App and are placed in the Sync Grid. Do check out this article if you haven't paired the lights to the App yet. If it's disabled for whatever reason:
Head on over to the Sync tab on the Lumos App.
Then scroll down to the bottom of the page and click on Grid Settings icon.
Toggle All Power Off on.
After it's toggled on, simply switch off any one Firefly light and the rest will follow suit.
An 'All Power On' feature is currently in the works. There are a few kinks that we're sorting out with this but do keep an eye out if we do release it in the future!