Service Berry Tree W/Spots
The growths you are seeing there are called lichens. They are harmless to your trees and are actually a sign of good air quality.
They are an interesting organism. You can learn more about them here:
These trees are about 20 years old. What would cause a decline and how should we treat them! They dropped leaves early. I also have a young Service Berry (about 3 years) that had dropped leaves early and also has lichens. Should we treat or fertilize?
We are still suffering a record-breaking drought. Serviceberries like moist soil. Water, water, water.
This drought has extended from summer into fall. Fall droughts can be killers if the shrubs (especially evergreens) are allowed to go into winter in dry soil.
Serviceberries are actually shrubs, of course. They will not live as long as a shade tree. Age may be making them vulnerable, as well as the drought. If they have already dropped their leaves, that indicates stress. Hopefully, they have not declined so much that they cannot pull out of it. (Fertilizer is not medicine and will not solve this. Some compost around the base--not piled on the trunks--should feed them enough.)
As long as the branches are still flexible and when you scratch the bark there is green underneath, there is still life in your serviceberries.