These look like shore pines (Pinus contorta).    Shore pines are very well adapted to the normally dry summer & early fall along the Oregon Coast so it is less likely that lack of water is the problem.    Overwatering can be an issue if the trees are surrounded by lawn that gets regular watering.

This could also be salt spray damage.  Sounds possible based on the description of your proximity to the ocean.   See page 4 of this Oregon State Extension publication - "Common Insect Pests and Diseases of Shore Pine on the Oregon Coast" - https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9008.pdf         

Table 1 discusses "Major Nonbiological Problems of Shore Pine".  The first one listed is salt damage.  Take a look at Figure 7 which shows salt damage to shore pines.  Note that it usually occurs on the windward side of the crown.   Trees often recover from this.

There are potential other possible causes that are discussed in the above publication.  Take a look at the symptoms/signs and compare to what you're seeing on your trees.