That is a sign of either a needle blight which is usually caused by a fungal disease, or possibly a lack of moisture reaching the top. The lack of moisture can be due to dry conditions, loss of roots from soggy soil conditions which exclude oxygen from the roots, problems with roots encircling the trunk which in a few years after planting will begin to strangle the trunk showing drought symptoms on the above ground parts of the tree.
Check soil moisture, dig down around the base a few inches deep to look for an encircling root (there is no way to practically fix this), and if need be take some affected branches to your local Extension Office to see if they can diagnose a foliar disease and recommend an appropriate spray.
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