Before sending this to a diagnostic expert, would you please take a couple pictures from about 5 inches away from some of the needles, showing them turning from green to yellow? 

A plain cardboard held behind the branch will help the camera focus on the needles. The pictures must be very clear to be helpful. 

Also, was any chemical or fertilizer applied to the surrounding grass or the trees? 
Is there any damage at the base of the trunk?

I will watch for your updates 

Thank you.