So I have some kid characters I've been working with, and some of them have this issue with their mouths I can't figure out and can't find answers to here or on Google. 

Their mouths are pinched weirdly (widen mouth" just makes it worse) and when they smile, there are weird black marks on the sides of their mouths. Here's a couple screenshots:

70% of original size (was 722x912) - Click to enlarge

70% of original size (was 722x912) - Click to enlarge

No matter what I do, I can't get the mouth to look right. I used the baby avatar and "aged" it to get the kids, so I can't imagine it's an issue with them being kids... why ideas? Thank you!

I'm seeing that her bottom lip looks seriously swollen too, but there's no way to make it smaller. The only lip slider is for both lips at the same time. How did it even get this big? UGH!!!



70% of original size (was 722x912) - Click to enlarge

It posted the same reply twice. Disregard.

Those looks like teeth/gums are pocking through the face skin.

Work with the teeth morphs scaling/pushing/fitting them properly.

Alternatively, use Edit Mode for character, grab Mouth corner faces or vertices and pull them out a bit with enough Soft Selection Radius and Bias.