I agree with camille on this. If the pseudobulbs are alternately wrinkling and plumping, they need more water. Eventually, they may get to the point where they are too old to plump up, but they will still store food for the rest of the plant. And definitely post some pics for us. They help a lot.
Speaking of which, I have my own oncidium pseudobulb related question. I have an Onc. Twinkle in a 4 inch pot with fine fir bark. It gets "weakly weekly" feeding and receives about 3-5000 foot candles throughout the day from a south window. However, it was growing in a dimmer west window for most of the time I've had it, closer to 2-3000 footcandles most of the day. When I bought it, it was crammed into a 3 inch pot, so I crammed it into a the 4 inch pot. There was such a wide mass of p.bulbs that I couldn't get it deep enough in the pot. The p.bulbs that grew after it bloomed are about a 1/3 or less the size of the growths it had when I bought it. There are about 8 or 9 crammed between the older p.bulbs. Also, the basal leaves failed to form properly and the few that did grow split when the p.bulbs expanded. Some of the leaves on top of the bulbs are pleated or disfigured at the base. It didn't seem to put out many roots either. Ok, I think that's a long enough description
, unless I missed something. Here's some pictures:
So should I repot or divide or something else?