Whats happening to my conifers - going brown

I have planted 13 conifers around my garden, however 4 of them have went completely brown.

They have all been watered the same and planted in the same compost, is there anything i can do to save them?

 

Looks like they are gone, dont think you have much hope in saving them afraid.

How long have they been in for?

 

I'm afraid they are as dead as a Dodo. Have you had other things planted in the areas before? The fence looks pretty new, maybe during it's construction something contaminated the soil in certain areas ? I'd suggest you take the trees out and dig down to see what maybe lurking below. Certainly I'd do a fair search before you spend money replanting new trees.

 

Conifers suffer in windy locations but I think yours have died to rapidly for that. There is a conifer disease that's been attacking them in the last few years, but of course that's not necessarily what yours have suffered from.

https://www.rhs.org.uk/advice/profile?pid=733

Sadly any conifers that suffer from die back tend not to survive as they can't replace there branches.