I've read that hibiscus do NOT work well with high bloom fertilizer, like most show plants do. They prefer the middle levels of nitrogen, LOW levels of phosphorus (no superblooms or bloom boosters), and high levels of potassium. Personally, I use 20-20-20, but I use it every week or two, - depending upon the rain that we get. Make sure that they get plenty of sunshine. Mine are flowering continually, and are loaded with buds.

What about outdoor hibiscus?