(I'm positive that no parents at our gym have any concerns).
THE single most important thing to understand about coaches who sexually abuse athletes is that abusers groom the community around them, especially other adults, so that no one has concerns about the abuser. One of the greatest risk factors for an athlete being abused is parents who trust their child's coach to the point that they can't fathom that the coach wouldn't abuse an athlete. There's a line between trusting your children's coach/teacher/youth activity leader and acknowledging that you can't know that an adult wouldn't be inappropriate with a child or especially a teenager.
Children and teenagers tend to disclose grooming in very small bits and it's often interactions that can be explained away. By the time grooming advances to outright abuse, the child/teenager has "heard" that their parent trusts the coach more than the parent trusts the child's subjective experience of being uncomfortable.
I'm not saying that your trust in your child's coach is misplaced or that you should have concerns. As a survivor of sexual abuse by a coach who watched several teammates be abused by another coach and now works in CSA prevention, I want every parent reading this to understand how fundamentally important it is to understand that if your child or one of your child's teammates is being groomed or abused, the coach will have groomed you too so that you don't have concerns.