Steph, it's beginning to look like a possible over watering or inconsistent watering problem.* These shrubs WILL tolerate full sun but do better in part shade.* Full sun should not cause their demise if they get proper watering, but can cause sunburn if they were previously grown in shadier conditions.* With sunburn, a shrub like this would usually show symptoms with brown crisp leaves and* by losing them.* Many areas of Colorado have drying winter winds and that could have also contributed to the problem over the winter.***
In looking at your pictures it's difficult to tell just what is going on, but it does look like a possible fungal problem, which suggests overwatering to me.* If you read 'Water Requirements' under 'Growth Conditions' at this link, you will note that it says to water when the top 3" of soil is dry.* Btw, the stems get a purple color when they mature.
I would suggest you have the landscaper who installed them take a look at them with the idea of possible replacement.*
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.