Both dim headlights quit working at same time, both brights headlights work fine. Fuses are ok and the relays in fuse box control right side and left side. There is no relay for brights and dims.
Have you looked at the lights to make sure the filament is still good? It is feasible you lost both headlights at nearly the same time. It's also possible, you didn't notice one of them had gone out (you mentioned they were dim ... a single bulb would have looked like dim bulbs) before the second one went out. Look for black spots on the bulb. Also, don't handle bulbs with bare hands, as the oil from your skin will kill them quickly (if the bulbs are still good).