when i bought it, it was beautiful and fully open. the lfs has another and all the heads have died off except 2. try moving it, they like medium flow but not alot. have noticed they wont fully open all the way w/ a ton of current. i have it in a 125 w/ 3x150w mh, 4x96w pc. the placing is about half way up under one of the halides w/ low to med flow. also suppliment the tank w/ phytoplex and microvert. if it doesnt open up all the way, there very well may be something wrong.
what kind of lights do you have and wattage?
what kind of flow is it in?
tank parameters(cal, alk, ph?)
do you feed it?