This year my rose of sharon, I have four, didn't bloom like they did last year and the year before that. One of the rose, Lucy, did the worst. Lucy, the name/type of bush, bloomed early this year and then it begins to lose leaves like it's going into dormant stage for winter. Leaves turned yellow and hardly bloomed, maybe 5 blooms on the entire tree. Lavender Chiffon and one of the Blue Satin didn't even bloom, just made leaves. I recorded all the fertilizing and watering on all my plants. Everything in my yard bloomed except my rose of sharons. I live in zone 7.
Rose of Sharon
Certified GKH Gardening Expert
You may have over fertilized. To much Nitrogen in the soil will cause lots of lush green leaves but no flowering.
You could do a soil test to take the guess work out.
Adding Phosphorous with a fertilizer like Bone Meal will boost flowering.
Here is a link to refresh you on care requirements.