Azalea have sooty Blackmold on leaves and stems
First time, I have at my home all Azhalea plant leaves and stems have powdey Black Sooty mold and some dendralions are dying and have white fungus on stems
There appears to be a scale insect pest (white spots on the stems). The scale is a sucking insect that excretes a sweet honeydew on which a 'sooty mold' grows. The sooty mold is not harmful except to shade the leaves from sunlight, but the insect pest at this level is a serious condition.
I believe the plants are susceptible to the pest infestation due to nutrient deficiencies, indicated by leaf discoloration which is characteristic of poor soil fertility.
I recommend that you fertilize with a slow release complete organic fertilizer like the Dr Earth Acid Lovers on this page:
Professional applicators would soil drench with a systemic insectide with dinotefuran
I'm not sure about the other plants. The white material could be lichens or a fungal secondary growth on the dead stems, and not the cause of the mortality.