Sick Box hedge

I have about 60 box plants, planted by a concrete walkway, south facing. The plants are basically not growing and very "orange" in colour despite being mulched, fertilized, watered as appropriate. Does anyone have any idea how to "turn" these plants green and get them to grow. Photos attached. These plants have been in the ground for approximately 4 years. Thanks for whatever advice you can give.

 

Why have my box plants turned orange????? - Page 2