There are also some black spots; we sprayed with orthanex. the bush has lots of blooms, it is in a container which receives morning sun and sun all day long. I have two of them, bought at the same time and same grower. One doing well; the other gets lots of yellow leaves DAILY - - if this keeps up, there will be no leaves!
It is in a miracle grow moisture control soil mix; we feed it miracle grow also since hibiscus are heavy feeders. We have had a lot of rain in the last two weeks- maybe 6 inches. BUT the other hibiscus is out in the rain, too AND I have two more on my back patio with no yellow leaves.