This is the second try on planting arborvitae in the clay we have in our backyard. The landscaper who put in the first 5 the autumn of 2012 dug them up and replaced them. Before he planted the new ones last autumn he mixed the clay with other soil (not sure what). These are also dying from the bottom and inside and look terrible. What should I have done (what can I do now) to help them grow and look healthy?