There could be several causes for drying or dead leaves. Most of the time the plant is still treatable; consider the following reasons for drying leaves:
Wind and extreme cold can damage the leaf, causing them to dry, turn brown, or dieback. Plant the bottlebrush in an area with wind protection else the wind will cause extreme dryness and the water to evaporate quickly. The bottle brush is damaged when the temperature drops below -6 degrees Celcius. In this case, remove the damaged leaves by pruning the stems.
Iron deficiency causes the bottlebrush leaves to turn yellow and restricts the growth leading to dry and dead leaves. Iron deficiency is caused by compacted and improper watering. Applying iron chelate to nearby soil will solve this problem.
Armoured scale, a bottlebrush pest can also cause dry, dead leaves. They feed on the sap in the leaves and stem. For a small infection, prune the infested branches. For severe infections, place sticky traps on affected branches and spray the leaves with ready-to-use horticultural oil spray. Inspect the plant and continue the treatment for ten days to completely get rid of the pests.