Thanks for writing. I'm sorry, but without being able to see your hibiscus and where it's growing, I can't say what the problem is. Is it possible you've made the soil too acidic for the plant? How often do you feed it? Too much fertilizer can be more harmful than not enough.
Do you have it growing in a container? If so, have you repotted it? If not, it's possible your plant is rootbound and stunted from that?
---Justin, Senior Garden Editor, BHG.com