Camelia brown areas
Thanks for you inquiry. It's difficult to tell exactly from the photos - however, my first guess would sunscald especially for the 2nd and 3rd pictures. If camellias get too much sun especially during extreme heat events then the out portion of the leaves can become "burnt" or washed out looking. The first picture look suspicious for a type of fungal leaf spot - there looks to be concentric rings within the leaf spot on that camellia. A broad fungicide such as Daconil (chlorothalonil) would help alleviate the presence of any fungal pathogen that could be present.
See the link below for more info on camellia diseases and insects.