NightFire Problems

Hey guys, Before I came across this great site I had purchased a NightFire hibiscus from a local hibiscus nursery here in Ft lauderdale fl.
It was in a 4in pot small plant. The plant looks good but it hasn't grown I had it for 6 months. I now see its budding and 2 flowers bloomed but they dont open. Anyone know why this would happen? I also purchsed another from him the same day and that plant also hasnt grown.
I only purchase from hiddenvalleyhibiscus now the plants I get here grow fast and look great.