I have two bathroom light fixtures that stopped working. At first, I thought it was a loose connection, as I pushed up on the light and they both came on. But after I tightened everything, it won't come on at all. I don't think the lightbulbs are bad (would 1 bad stop both fixtures, and the other 5 bulbs to not come on?) We used to notice one of the bulbs would flicker ever so slightly, no matter whether we loosened or tightened the bulb. Any help would be appreciated.

I have seen a "Arc flash" in one bulb kill six bulbs in a candelabra.

Start by replacing all the bulbs in one fixture and then the other.

Bulbs are good. Any other ideas?