its probably just the filament. you can blow just the low beams on both (happened to me) but if it is the filament and both low beams blew at the same time you might wanna get your alternator checked out. mine put out too much power and blew the headlights, ecu, and a bunch of other stuff you don't wanna replace.
Use a multimeter and check your connector for power on the low-beam line. If you are getting power but the bulbs are not coming on then it means the filament is blown as was suggested before. Bulbs are cheap if you're using stock bulbs, so just get one and try. If you're sure the fuses are fine I'm assuming you used a multimeter or a tester of some sort - use the same one to check for the power on your low-beam line.