My standard Cymbidium will not open

[tomp]

I have around 10 plants each of a 2 culivated 30 year old cymbidium plants. One miniature and 1 standard. Right now the miniatures are blooming all over the house. One older plant has 10 stalks of blooms. The standard is the ones giving me trouble. They first started to set the bloom stalk in December and the will not open. They get alomst ready to open and then they start to die. I have them in all kinds of different normal light, feed them twice a month and water weekly. These standard started to do this about two years ago. Before that they would bloom just as nice as the miniatures. Any help I can get to get these plants to open their buds would be appreciated.