Dying Conifer?

I planted 10 conifers (18") 5 years ago and they're all 7' now. 

In the last couple of weeks the end one (closest to the fence) started browning from the base and has quickly wilted to the middle. 

We have a cat that visits our garden but other than that, I'm not sure. They get watered but it's rained quite a bit recently, so they shouldn't be dehydrated. 

Does it look like a cat problem or a disease etc? And mainly is it reversible? 

Thanks.