Q.My Bottlebrush Tree And Shrub Have Got Dark Brown Leaves Will It Recover ?
What can I do to encourage new growth when the leaves are brown. This occurred on both my tree and shrub, or doe I cut it down and hope for new growth.

Certified GKH Gardening Expert
Unfortunately, your photos did not come through, so I am unable to see the extent of the damage. Unfortunately, it does sound fungal or bacterial in nature. In these cases, treatment will be difficult. Whether it is fully treatable will depend on the particular disease, however.
https://www.gardeningknowhow.com/ornamental/shrubs/bottlebrush/diseases-of-bottlebrush-plants.htm
I would advise treating with a fungicide. This article will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
This collection of article will help you with the care of your shrubs:
https://www.gardeningknowhow.com/ornamental/shrubs/bottlebrush