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
Certified GKH Gardening Expert
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.