By far, the most likely explanation for this browning is that the conditions are not allowing the plant to get enough moisture. Conifers are generally hungry and thirsty. Browning often occurs when the roots are not taking up enough water, and when the plant is exposed to cold drying winds – stopping the plant taking in moisture through it’s greenery. Remember that the natural habitat of conifers is very mild damp woodlands, where protection is in vast numbers, and the climate allows for plenty of moisture.
Have a go at resolving this issue first, although you will find that it will be a good year or so before it recovers.
There are other problems that could cause this – but with the info given, I’d probably go with that.
but it could be due to “Conifer Die Back” . Not likely unless you’ve trimmed them to much.