Oncidiums, with their soft, thin leaves, are especially susceptible to various things which cause spotting on the leaves. I don't think the spots on your leaves are the blacks spots which appear in high light. They are too large and irregular. I do think it is the result of some type of infection, but I don't think you need to worry too much about it, because I think with proper culture, the problem will resolve naturally. The spots won't go away, but I don't think it will spread aggressively. I think treating it with a bactericide or fungicide would be a good thing to do just to make sure, but I don't think it is strictly necessary at this point. If you choose to do this, I think Physan 20 would be a good choice. It's a good idea to keep that on hand, because it is useful in a variety of situations. If you don't have that and don't want to buy it, treating the leaves with hydrogen peroxide might be helpful. It is true, however, that Oncidiums and their relatives just tend to have spotty leaves, and I don't think you need to be terribly worried.