Are you watering these trees? Watering is important for plant establishment. It's possible these trees, and especially the one that is struggling the most, are suffering from transplant shock and/or are having trouble getting established. 

If you are able, run a hose at the base of each tree ~ once every two weeks or so. We have had some breaks in rain and warm temps that can contribute to the struggle to get established.

More information here: https://www.canr.msu.edu/news/dont_forget_about_newly_planted_trees_and_shrubs

That possibly may be the culprit. You can dig down and inspect the roots to see if they look healthy (white and firm) or if they are brown, mushy, brittle and unhealthy looking. 

I am also wondering if these were planted as ball and burlap plants. If so, was the burlap removed at planting? Burlap, especially synthetic burlap because it does not break down, creates a barrier that makes it tough for the roots to grow outward and for the trees to get established.