It could be as simple as iron deficiency. I wouldn't re-home them just yet. They look fine to me. Not everything is beautiful. Laotse said that for there to be beauty, there must be ugliness. Something like that anyway. Only been one perfect. Ever. Enjoy what they have to give you and let them live. Dang I'm really jonesin for sashimi right now. Back in a bit. Sushi run.
I give all my plants the same stuff (that contains iron by the way) the same amount. I don't know why certain oncidiums show spots on the leaves while others don't.
Also, as I understand, iron deficiency shows up as yellowing of leaves, usually leaving the veins green.