Is my tree going to die?
Thank you for contacting us. There are a number of possibilities to explain the die-back on your tree. The fact that your neighbor's trees are adjacent and similarly affected indicates there may be a root problem or disease. Due to the size of your tree, I suggest you consult with a certified arborist in your area who will be more familiar with diseases on your particular species.
I'm sorry I cannot provide more assistance, but I am in Ontario where our weather, species and diseases are different.