Why yellow hibiscus new leaves?

Question

All the new leaves of our common red hibiscus are yellow. The same thing happened last spring too, and the leaves later became green, as were all later new leaves.
We live in southern South Australia, the hibiscus is on the north side of the house but most of the lower parts (which are where the new leaves are) are shaded by neighbour’s trees until mid afternoon. It is about 5 metres high and could be thirty or so years old. Can anyone suggest why the yellow leaves, and if we can or should do anything about it?

Answer 1

This article will help you pinpoint the cause.

https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/answers-to-what-causes-hibiscus-leaves-turning-yellow.htm