Thank you very much! You have been very helpful :)
The first thing is to try to figure out what's causing the brown spots - there are many possibilities. Examine the brown areas for damage to the branches. If nothing is broken, check for insects and/or sticky areas.
There could be tiny aphids or scale attached to the branches and underneath the leaves, or spider mites, which spin tiny webs on the leaves; you can see this if you spray some water on the leaves with a spray bottle. This article has info on these common pests (I know the article in about houseplants, but the bugs are the same inside or out:) https://www.gardeningknowhow.com/houseplants/hpgen/common-bugs-and-pests-on-houseplants.htm
If not bugs, consider the cultural requirements of the viburnum and how they are being met. Is it too wet? too dry? too much sun? too little? Also, since you planted it only last summer, perhaps there was a problem in transplanting. These articles will give you some things to consider: https://www.gardeningknowhow.com/ornamental/shrubs/viburnum/viburnum-shrub.htm
You can also get help and advice through your master gardeners assoc. This link will help you find the nearest group: