Brake lights

This is a very unnecessarily-complicated circuit, and it gets worse if your vehicle has the optional "dynamic laser cruise control". The good news is your observation of the center high-mount brake light working proves most of the circuit is working. There is very little between that lamp and the left brake light. Any single defect should cause all three brake lights to be dead, or just one of them. There is not anything I can see that would cause just two lights to go out.

Lets start with the left rear brake light. If the left tail and turn signal bulbs work, we know the ground circuit is okay. Back-probe the green/white wire at the connector. You should find twelve volts there when a helper pushes the brake pedal. Let me know what you find.