it sounds normal, bamboo often will produce more shoots than it is capable of sustaining in case some are damaged by browsers, weather etc. once the plant has elongated as many shoots as it can sustain, it will simply abort the rest. the aborted shoots generally seem to stall out at a certain height still looking good but at some point if not needed they just rot away. the cause on yours could be something else but this is the most likely scenario.

I cant thank you enough. You really put my mind at ease. Jane