Hibiscus Leaves Have White Dusty Covering With Buds Turning Yellow And Dropping Off Bush

Question

Also, One bush’s leaves are yellow

Answer 1

Sounds like powdery mildew. It is very hard to get rid of once it takes hold. Here is more:

https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-has-white-fungus.htm

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