Oncidium - yellowing leaves

[kdaniels8811]

Hello everyone! I have an oncidium I bought mail order - it came in bloom and bare root. I immediately potted it in bark and soaked the bark so the roots recieved a good drink. It has been about two weeks and the leaves are turning yellow. Just one so far but yikes! What should I do? The bark is cool/damp down about an inch. The care sheet says not to let it dry out, should i water more even though it runs right through? Any advise is really appreciated.