Many people call anything that stays green in the winter a pine, are these really pines, and what kind? Also it will be helpful to know what kind of stand they are growing in, are they in a lumber production type stand, or part of a formal landscape?
To diagnose, the trees you need to look at are those that are just becoming symptomatic. Once a pine under goes some kind of stress, it's very common for secondary pests to move in, like boring insects. This makes figuring out what is wrong hard because your expert comes in and sees a tree all chewed up by insects, but the original problem may be completely unrelated.
The number one killer in landscape trees, has to be environmental problems, like compacted soil, trenching, planting depth, and stuff like that. In forests, it's a different story.
A few pictures would be worth a thousand words.