All lack of comprehension in our classes by our students is entirely our responsibility. If we ask too many questions, the sounds overwhelm them and they bog down. If we speak too fast, the speed overwhelms them. We are the only ones in the classroom who can control these things.
A few fast-processing kids will falsely make us think that all of the kids in the room are getting it. This is a disaster for the other kids in the class. Learn to deny the faster processors something they have very often done in all of their classes: ruin the class for the other students.
Do not teach your CI classes in ways that exclude any students. The StarChart™ works to that end, toward full inclusion of every child in the group, so that the primacy of the community is what defines your instruction, because when community is the focus in a language class, only good things happen.