cedars seem to be dying

by Don Beam
(Guelph, Ontario, Canada)

4 year old 6-8 foot cedars greenish on bottom and top .. brown in middle. There are 18 of them that were planted at the same time in a trench.

These cedars were planted by an Nursery, in rocky, sandy soil with some triple-mix added to the trench.

First year all was well .. ever since they seem to be dying a little each year.

The branches are brittle and even the green areas are very dry to brittle.

These have been watered and have had evergreen spikes added in the last 2 years.

They have not been wrapped.

The Nursery is at a loss .. so are we ... any ideas