It could be winter damage. It could be sprinkler hit this area and it is staying too wet and go a disease. It is expanding? I would prune it out and with time should fill back in. This link might help you. https://ask.extension.org/questions/447205

location .. big city name will help us help you .. e.g. any current local plagues..etc ...

if the plants are IDd ... then you can contact your county extension office regarding local problems ... should we fail here .. which i doubt ...

ken

The original post is 2 years old!! Responding now is unlikely to be much help to the OP at this late date.........

FWIW, cross-posting to Ask the Yard Doctor is likely why this query received no responses initially. Anyone who accesses this website via GardenWeb is unable to respond to that forum. It was never intended to be a discussion forum and that trait has held over through the years. Houzz admin should really just remove it as it causes complications and the original purpose has long vanished into the ether.