3 weeks ago I purchased 2 lovely vibrant Cypress Goldcrest which I have planted as 2 specimens on the advice of my local garden centre expert who said they would be fine in my clay soil, since planting they have completely lost their lovely vibrant yellowish green colour and now look a dull green and some of the tips are turning a bit brown they look like they are slowly dying to me. What would cause this? Have I over or under watered them? They were planted in fresh compost, the ground around the tress is covered with a membrane to stop weeds with gravel on top. Are they salvageable or should I admit defeat? Any advice would be very welcome.