It sounds like your camellia is heat stressed. Even if it gets regular water if it is growing in a pot once the roots fill the container it is very hard to keep them cool and hot days can really stress out camellias especially if they are in containers. Try adding a thick mulch of wood chips on top of the soil and water even more often. In the fall you may want to consider transplanting the shrub into the ground  where the roots will stay cool. Keep growing, Marianne Binetti