Brown sky pencil holly
I planted my sky pencil holly 3 years ago and this year part of it started turning brown. Why? I planted 4 total and the other 3 are fine.
Virginia trees and shrubs
Many hollies will get Black Root Rot if water stays around their roots too long due to planting too deep, poor drainage, too much rainfall/irrigation. If the plant isn't all brown you could take a root sample and a branch that has both green and browning leaves on the same branch to your local extension office for free testing.