Low Beams dead, Hi Beam Fine?

Simple. Only thing "common" is the dimmer switch and the path of the low beam power wire..........From dimmer switch and connector, through bulkhead connector, one wire around headlight harness, splits and feeds both headlights.

OR the rare possibility that you blew out both headlights. "I spose" it has happened

Or a problem with your relay ........Where do they get their power? I don't know........"you" wired them