Luma devices are periodically updated with new firmware.
When this happens, you will notice that the light on each of your Luma will start spinning blue for a period of time. This should last for approximately 2-3 minutes. After which, the light will go away and the luma will return to its normal state.
Please note that during a firmware update, the Luma will also require a network/device reset and as such the Luma will be offline for the same period of time. This is approximately 2-3 minutes.