Sometimes we plant trees that are extremely sensitive to hot temperatures. Your Katsura  leaves have brown edges because of the high temperatures we have been and will continue to be experiencing this summer. Most sources I consulted  for this plant recommend sites with marine-cooled air, 25 inches or more of rain  for an average year ,and summer breezes that cool temperatures below the 80's. Those conditions do not  exist in our area. Is your tree planted in shade? This might help. Katsura is usually planted for it's lovely fall color and brown edges do not suggest that yours will make it to cooler times without a lot of browning out. It's unfortunate that some nursery  suppliers don't pay attention to the fact that the temperatures are rising and continue to tempt us to plnt exotic species which can't take the heat.