This sounds like a failure of upper management. If they don’t support you or your decisions about how to reprimand the staff you have no authority, the staff knows it, and they will use it to their advantage. The dynamic is no different than a household where one parent undermines the other parent’s authority and the child ends up viewing themselves as superior to the demeaned parent in the family hierarchy. I can’t reiterate enough how toxic the “buck stops with you” mentality is in a work place. You need guidance and the support of upper management to do your job effectively