I'd agree with other answer that it's more because of bad bulbs. But it is pretty weird that both left side are down. On the left rear light, do yo still have it illuminated with you turn the lights on? I know you said left brake light, but that's only when you press brake pedal. But if lights are on, is the tail light still lit? If yes, then it's just the bulb.
Good suggestion. You usually have to buy a pair of bulbs, so go ahead and replace the right side, too. That way, you know that both are brand new at the same time, and don't have to guess about which one is newer or not. Headlights are different. Don't have to replace both of them. Just when they go out.
If a fuse for headlight or fuse for taillights blew, the whole headlights would be out. And whole tail lights would be out.
