New Rowan tree seems to be dying

Our newly planted Rowan tree seems to be dying, it has a mixture of mostly brown leaves and some green but the number of brown seem to be growing. I've also noticed the bark on two of the branches has split. The tree was planted about 8 weeks ago before we moved into our new house, it was probably neglected and not watered during the recent hot weather, we got keys last week and have been watering it every day. Can we rescue it? Any advice will be greatly welcomed!