Yeah, my left one is a little lower than the right. It's definately normal
Why? First, your body isn't all symmetrical, so some things are gonna be different on one side than on other. The second reason is that usually, one testicle is heavier than the other. That's normal too.
The last thing I would say is that for some reason (who knows why), the tubes that connect to your left testicle tend to be weaker and can stretch easier, which could also allow it to hang lower.
And in most guys, for some weird reason, the left testicle is smaller but hangs lower. Weird, and again nobody really knows why