you might not be getting enough light and humidity for blooms. Not enough light is the number 1 reason orchids wont bloom. Humidity comes in close 2nd. The Bulbs look mature and should bloom with enough light. Go Easy on the high nitrogen fertilizer and use higher in the potassium range. You got to almost burn them things to get a bloom. The oncidiums and intergenerics I have seen come from the Hawaiian islands have purple/reddish bulbs and are blooming crazy plants. Of course we all cant provide orchid heaven type conditions like they can on a tropic island, but we can get close enough for a bloom.
I think oncidiums IMO need more light than catts to get a good bloom season. I am still a NOOB
so please take my advice lightly.
I been more of a fan of larger flowers rather than many flowers, so I'm not especially endeared to oncidiums.