I noticed my stutter around 11/12 years old. My dad would tell me to slow down when speaking, and it helped a little and is still something that I do now at 26 if I need to speak very clearly, but there are still certain letters or sounds that I will always struggle with. At this point I've learned to make jokes when I stumble through a sentence but I understand that it's harder for kids. Speech therapy is a good option to consider! I've always wondered if my stutter would be less of an issue if I'd gone to a speech therapist when it was first noticed. There is always a chance that your girls will grow out of it. My older sister had a pretty bad stutter when she was a kid and she's mostly grown out of it. It's absolutely something that can be helped with a little effort. Best of luck to you!