Generally, it will take two weeks to see the effects of the treatment, and the effect lasts three to six months. Over time, you may require fewer treatments because weaker muscles atrophy and require fewer injections.
The hibiscus is a heavy feeder that prefers frequent but light fertilizing. A nitrogen fertilizer in the spring and a high potassium fertilizer in the summer work well for the hibiscus plant. Also, fertilizing at the beginning and during the growing season gives the hibiscus needed nutrients for growth.
I received your fertilizers (special blend and hibiscus booster) a couple of weeks back after using super bloom for several months. Most of my plants looked ok at the time of the order but my preference is to supply the correct nutrients. A side benefit I was not expecting is my blooms now stay open for two days.