answer:Are you using compact fluorescent bulbs in those fixtures? Dimmer switches won’t work right with those. They’ll stay off until you turn the switch up to a certain point, then come full on. They might have gone off because you had the switch barely above that minimum, then something bumped it to bring it just below that threshold. No damage done. If you want the dimmer function back, you have to return to the old energy-wasting incandescents. I’m not sure if LEDs will dim or not. Welcome to ask-public!