Onc. gold dust not flowering completely

[HItransplant]

I have an onc. gold dust that is pretty small (2 in pot) and had 2 spikes on it when I picked it up, one more mature with buds, the other with no buds at the time. I have been watering it once every week and feeding with 6-30-30 fertilizer at 1/4 strength each time I water. The pot is also sitting above a moisture tray as the humitidy in the house is pretty low (forced air heat). The buds on the older spike have flowered and the ones on the younger spike are getting fatter,..the problem is that this is only happening at around a 50% rate. The other 50% of the buds have dried up and are falling off. Other than this, the plant looks healthy and happy.

Whats happening? ... is it not getting enough nutrients, or is this normal?

thanks for any help with this issue.