My hibiscus is outside. Was blooming beautifully and now has a few blossoms, but the leaves are turning yellow and dropping. I had given it Miracle Gro a couple of weeks ago and we have had lots of rain.
Certified GKH Gardening Expert
The following article should be of some help to you: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/answers-to-what-causes-hibiscus-leaves-turning-yellow.htm