All of a sudden both of my headlights are not working but Brights do work.

Failed headlight bulbs or fuse... Simply test for battery voltage and ground at the headlight wire connector.

There is a relay that controls both low beam headlamps, if both went out at once that is likely the cause. There are also separate fuses for each light after the relay. It can sometimes be difficult to tell if both went out at the same time or if you were just used to only one being on and then the other one when out and you noticed it. If thats the case bulbs or fuses could be the problem, but if they both actually went out at the same time it's probably the relay (or something in the switch or wiring) that caused the issue. Also, on some of those gmcs theres a headlight dimmer that has a fuse before the relay that could cause that but I think thats fairly rare.