Having all my characters sound the same is a big worry for me. I wonder a lot if dialog comes off authentic. When I wrote two high school students, I didn’t put in cursing in, but I personally didn’t want to see it in my writing, but then realized that wasn’t how my kids talked, except around me and other adults (mostly). Around their friends I’m sure they swear up a storm. Even after making some adjustments, it took me a while to get used to it. I guess I just find it hard to be casual with my dialog sometimes. I’ve done so much formal writing that it’s hard to break.