Thank you for reaching out to ask2.extension.

There is a disease that boxwoods are susceptible to because they have been so over planted.  It is starting to be suggested to find an alternative plant.  

It could be your soil, but I’m inclined to think it’s not.  The only way to tell for sure is to get it tested.  You can find the process by going to extension.umn.edu and searching for soil testing.