Are you providing supplemental irrigation? Were they watered well in the fall to get the roots established? Do you know if the burlap was removed at planting time or the roots loosened if they were container plants? 

It looks like they were planted in surrounding and existing tree roots, were they planted with any soil amendments or needing to be fit into a small space around roots? 

You can look at the base of the plants to see if you notice any borer holes or other problems but if there are only a few that seem to be failing then it could just be that these failed to establish over the others. You can refer to our Cherry Laurel diagnostic page to examine the plants more carefully or be on the look out for other symptoms on the existing plants to look out for. 

The photos of the plants in question look pretty bad though and we would suggest removing them and replacing as they don't look like they will be able to recover. 

Emily