Thank you for your camellia question. I believe your plant may be infected with either a fungal or a bacterial pathogen. The yellowing may be from a lack of nitrogen, which has many causes, including inadequate nitrogen (fertilizer). However, camellias can also suffer from sudden oak death, and examining the leaves under a microscope for signs of it would be helpful. Totally brown leaves can be a symptom of camellia dieback.   In order to get a positive identification, and assistance with control(s), I suggest that you take a branch with leaves, healthy, brown and yellowing with spots, to the Washington County Extension office. Perhaps with their superior examination equipment, they can help better than I.  

Their address is 1815 NW 169th Place, Building 1, Suite 1000, Beaverton; phone<personal data hidden>.)  I hope they can assist you.  Good luck!

Thank you so much! 

You're welcome.  I just edited to clarify where you're going.  Best!