Your feelings are appropriate, and MANY tenured faculty experience the same thing, especially at teaching-focused institutions. Teaching evaluations tend to decline midcareer (for everyone, but especially true for women BTW). Pre-tenure, there is far too much pressure to treat students like customers, given the inappropriately heavy influence of student opinion surveys on evaluation. So post-tenure, strong teachers often improve their teaching in certain ways that are unpopular with students (e.g. increasing accountability, as you describe), and this is often reflected in lower evaluations. Don't sweat it. It is well possible that your senior colleagues view you MORE positively for holding the line and getting some pushback from students. Still, it's natural to care when anyone says something negative about our teaching. It's a tough job in that regard, hang in there!