Oncidium PBs growing smaller?

[King_of_orchid_growing:)]

I disagree that your plant is slowly dying. I think it is the exact opposite. You must look at things in context, and you must have some experience under your belt to know the difference between a plant that is developing, and a plant that is in distress because the signs are oftentimes very subtle and can be difficult to verbalize and tell apart. Proper diagnosis comes in context of the situation, not out of it.

Your Oncidium Twinkle 'Fragrance Fantasy' looks fine to me.

As Oscarman had mentioned, the pseudobulbs do not reach their full size potential until the growth is fully mature. The size of the pseudobulb at the time that it is first developing will not be how large it ends up being. That new developing pseudobulb could end up being slightly larger to significantly larger than some of the preceding ones.