Is the damage only on the old leaves? If so then it could just be part of the leaf dying before it falls off. If the damage is on the new leaves also then I think you have a disease problem and my guess would be bacterial - but that is just a guess. There are sprays but they don't do as much good as just plucking all the infected leaves, pruning out the infected branches and cleaning up the area around the bushes and taking extra good care of them until they bounce back (throw everything away, don't add it to the compost pile). My attitude is usually that if a disease is fast moving and seems to be overtaking the plants then anything I spray isn't going to get to work in time. Helping the plant get healthy seems to help them recover stronger. But it takes time and it takes work and there are many diseases out there. Most viburnums are pretty tough in my experience.

We have 5 of these planted as a hedge. The plant will look like this each Spring before new growth starts. I guess it's the old leaves getting ready to drop. I was so worried the first time I saw this, but now it's so common each year. We planted them in 2009. Good luck with yours.