Yellowing then browning Oncidium leaves!! Physan 20?

[greenpassion]

I had posted earlier about the leaves on what I believe to be an Oncidium turning yellow, but now they are browning too. It's two 'outer' leaves, not new green ones, but the leaves look ill to me, not just aging. They are yellow along an edge first, then browning, with little spots along the areas turning color. I just used some physan 20 that I had recieved in the mail today but I'm really shooting in the dark. Now I'm worried that I used too much or something. I mixed according to directions, and sprayed all the leaves and surrounding areas. I tend to learn by trial and error, but I don't want to ERROR!!