Wi-Fi devices may appear offline in the respective app from time to time! There is no need to reset the bulb as a reset would break it's connection with your Wi-Fi and require you to delete the bulb from the app and perform set up again as a new device.
You can check the following steps to bring the bulbs back online:
1) Please check the light switch and make sure the power is On.
2) Power cycle the Wi-Fi LED bulb, wait 1 minute and check the status.
3) Please check your home Wi-Fi network and internet connection is working properly.
4) Try moving the bulbs closer to the Wi-Fi router.
5) If all else fails, try to restart your Wi-Fi router.