I have a degenerative problem with one of three barberries that I planted at...
We cannot make an accurate diagnosis from your photo. We only see a partial photo of the declining shrub. If planted this year, most likely the shrub declined due to poor drainage, poor soils, root system not establishing itself, drought, etc.
Barberry is an invasive plant and we do not recommend planting them. They spread by seed and vegetative means and displace our native plants. Barberry seed is transported to new locations with the help of birds and small mammals which eat it. See the link from Weeds Gone Wild http://www.nps.gov/plants/alien/fact/beth1.htm
You may want to take the opportunity to plant some native species as a replacement.