People with 3.5-4.0 GPA shouldn't really worry too much about their grades for applying to grad schools, except for applying to the top tier (but these are hard enough to get into that any student would be worried). You don't need a 3.5+ GPA to get into grad school.
It might be important to note the people who post on this forum are not representative of all physics undergrads/grad school applicants. I think the profile threads especially show a bias towards the stronger students (either the average student is too intimated to post, or does not know about this forum, or is not interested in posting etc. who knows). I visited a school this year with a couple dozen other students but none of them posted an acceptance in this forum (i.e. I didn't see such a profile posted in the 2012 thread).
GPAs in the 3.0-3.5 range are still "good enough" for grad school -- maybe not for the top tier schools though but it really depends on your program. I suppose if you are worried that your grades don't reflect your ability, maybe a strong PGRE score will help (but there's no guarantee that your PGRE score will reflect your ability either!).
If you and other students think you have a case for unfair marking, you could try to approach the department but any changes to how the courses are done probably won't happen until after you're gone! But if Western Washington is known for giving out low grades / have hard exams then you can only hope that the schools you are applying to knows this. I'm not sure if mentioning that your classes have a C- average will help you since with just that information, it's not clear whether this reflects the courses' difficulty or the students' ability or some combination.