Hello and thank you for contacting Ask Extension. From your pictures I can’t tell for sure if there are two trees planted there but the one on the right looks dead and I don’t believe there is any treatment that will bring it back. I would cut off the dead/brown part and see if the other tree makes it. There are several possibilities that could be causing the browning needles: lack of water, too much water, de-icing salt run-off, insect or disease problems. There is not much space between the wall and the sidewalk so whatever you plant there needs to stay small. The reflective heat off the brick wall in combination with a lack of water is my best guess at what is killing your evergreen.

If you want to know for sure what killed the one tree you could send in some samples to the Plant and Pest Diagnostic Lab at Michigan State University. Here is a link to their website where you can find information about how to submit samples, their fee structure, and a form to include with your sample. https://www.canr.msu.edu/pestid/

If you decide to plant something else in that spot here are a couple suggestions for small native trees or shrubs that are tolerant to de-icing salt (since the sidewalk is so close): Michigan holly, Snowberry, Juneberry or Serviceberry (maybe too big for your space), Larix or Tamarack, Button Bush, Viburnum, Rose of Sharon, Northern Bayberry, Witch hazel, Spicebush, Inkberry, Elderberry.

Here are a couple links to articles that may give you some ideas.

https://www.canr.msu.edu/resources/smart_trees_and_shrubs_for_michigan_landscapes

https://www.uvm.edu/seagrant/sites/default/files/uploads/Salt%20Tolerant%20Plants%20Northeast%20Natives.pdf

https://www.canr.msu.edu/news/native_plants_for_michigan_landscapes_shrubs