Trees in western Oregon tend to get a lichen growth due to our climate (rain, rain, rain!). Usually it's not a concern, but lichen can grow more on stressed trees. Other than the lichen are you seeing any other symptoms like dieback in the canopy or the trees not leafing out like normal?
Young ornamental trees can benefit from fertilization. There is a great OSU Extension publication called Fertilizing Shade and Ornamental Trees which has a lot of details.
From this publication:"A common recommendation is to apply 0.5 pounds of nitrogen per inch of trunk diameter at breast height (4 1/2 feet off the ground)." I've attached a screenshot from Fertilizing Shade and Ornamental Trees that shows how you can adjust the amount of fertilizer to the size of your trees and the fertilizer you choose.
There are many different brands and formulations of fertilizer out there and some are sold as specific for trees and shrubs. These fertilizers aren't necessarily a different composition from others but will have directions on the package specific for tree/shrub applications. Some fertilizers work best when they are spread over the soil surface and others may require you to dig small holes around the drip line of the trees. Always read the label for proper application and handling instructions.
If you have specific questions that aren't answered in this publication or on the fertilizer label, please don't hesitate to get in touch!