What is eating this plant?
First please check for any evidence of insect presence, for instance insects in any stage of life, eggs on underside of leaves, frass (bug poop) on or under leaves. If you find anything try to get images of your findings and resend to us for further investigation.
If you find no such evidence I will say this looks like shot hole fungus or disease. Shot hole first appears in the spring as purplish or reddish spots about 1/10 inch in diameter on new buds, leaves, and shoots. Spots on young leaves commonly have a narrow, light green or yellow margin. The spots expand and their centers turn brown and can drop out, leaving holes.
Splashing water and/or continued wetness can spread the disease. To help with this water by drip, soaker, or low volume sprinklers with deflectors. Do not use overhead watering. Also water early enough in the day so that the foliage has a chance to dry out before evening.
Also, increase air circulation in the plant through pruning. You might need to get creative in terms of your hedge but the goal is to open up the interior of the plants to allow for more air circulation.
I refer you to the following article from University of California Davis.