camelia

HELP!!!!, I have a stunning 50 plus year old camelia. And this year its developed a mass of what seem to be black spots/ marks on the leaves. And around 10% of the leaves have started to yellow. Does anybody know what this might be, and haw to cure it.

Yellowing of leaves often indicates too alkaline a soil. Try giving a good feed of a food suitable for acid lovers or sequestrine of iron and see if that helps.

All my camelias have the black soot on them. 

That suggests that they have scale insect on the underside of the leaves - these excrete honeydew, on which fungus grows. Kill the scale insect by spraying with Provado Ultimate Bug Killer, wait a couple of weeks and you can wash the leaves clean.