I don't think you draw your mouths too low. For example, based on the two characters in the first picture, the male simply has a longer, thin face. He is in porportion, and then again, not everyone will have the perfect features. People in real life have eyes that are too wide or too close, they have noses that hook like a beak, or are too bulbous and wide, and others have chins that are longer than usual.
There's nothing wrong with the girl, from what I see, so great job there!
So if you wanted, you could simply pass off a character for having unfortunate genetical luck.
Then for your second character, all I see wrong with him is the nose. The nose could have maybe been drawn a little closer to the mouth. With the nose in the position that it's in, it's an unrealistic distance away from the mouth. (Your style is more realistic, so that's why I say that. If it were a cartoon, it wouldn't make any difference, because cartoon genetics can literally be ANYTHING you want. Think of Amazing world of Gumball, they humanized a piece of toast. See what I mean?)
So yes, all I think you could edit is his nose length in the second picture. Then he'll be in porportion (based on more realistic terms) and he'll overall look a little better.
And that's it! Other than what I mentioned, let me just say your art style is very lovely! Your characters look lovely and very interesting! Keep up the good work; I look forward to seeing more work from you!