Douglas fir trees appear to be dying.

For some years Fir trees in my garden (Dark Green Pines) and had brown areas and areas of no growth. Have cleared back a lot of this part of garden to give more light to these trees however it now appears that I have lost more growth on the trees. About 70% of the tree is now brown and has no green pines whatsoever. Is this tree unfortunatley dying in your opinion? I can supply photos if this would help.