We viewed your photos. We do not see many problems with these trees. It is possible you may be dealing with some winter damage but we cannot say for sure. We would like to have more information.
How old are the trees; how large were the trees when planted; how exposed are they to the wind; what is the drainage like in this area; were they planted as container or balled and burlap trees, etc.
If the trees were container plants, were the roots teased apart so they could grow into the native soil. If balled and burlap was the burlap removed or cut away at least half way down the root ball. Take a look at the planting process for more information.
The trees were planted about 10 years ago. They were only a few inches big at the time and have grown very well. The drainage in the winter is poor, especially this past Winter, but the ground is dry today. Looking at the trees today, the brown needles have extended further up to the top of the tree. I think it is dying. Could there possibly be a diesease spreading among those trees?
Poor drainage has killed a slew of trees in Maryland this past year and continues to do so, due to the abnormal rainfall in Maryland last year (twice the normal amount) and before.
Though the trees show no insect or disease, that's because this is an abiotic cause, namely, roots have drown. Loss of root mass eventually catches up with them and they die. Many trees got root rots from the saturated soils, and this killed them.
Evergreens often suffer damage but die very slowly. They are able to stay green over the winter because of cool temperatures and no pressure to grow. Spring and summer bring hotter temperatures (they lose moisture faster) and they are not able to put out new growth. Their reduced root system cannot keep up. This puts them into a spiral of decline.
If possible, improve drainage in the area. When you plant, plant slightly high (about an inch or so). Or select plants that can tolerate saturated soils for long periods.