My guess is also mildew. I have the same problem with mine that get some shade. The fungicide should take care of it. The leaves look ugly with the black, don't they?

I sure wish someone would answer this because I have the exact same problem. Had it last year and it affected all my plants and I'm seeing it again this year already.

Very possible that the little black fellows are aphids. If so, they suck plant sap and will weaken the plant. Rub them off, or use direct hits of insecticidal soap, diluted according to label directions. In both cases, repeat as needed. I'm not able to see enough detail to suggest what the white might be.

That packing of plants close together is worrisome but, unfortunately, I am not aware of what "vector" helps spread the darn thing from one shrub to another. Yellow mottlevirus, which affects camellias, has no known vector either while Rose Rossette Disease -caused by a virus- has a mite. This ring virus probably has something else so being close to an infected camellia increases the risk of getting it. And since you cannot tell if a camellia is infected (there is no test), you can look at one plant that looks healthy and after a while, it shows symptoms. That is why many people who bought healthy ones that develop the rings then decide to "live with it". In this case, I think they just prune affected parts if they do not like the look. The same happens with the camellia yellow mottlevirus although sometimes the yellow leaf variegation looks pretty to some people. I have seen some pretty and some not so in plants for same at nurseries.