One of the leaves on my Don is turning yellow is that normal for it to lose a leaf when it is establishing itself.
http://i168.photobucket.com/albums/u189/Dragom312/P2220031.jpg

Yes it is normal for plants to lose their older lower leaves. Is that garden plant soil the plant is potted in? If it is I would repot it in bark mix made specifically for growing orchids.

I will have to check I just left it in what it was sent in. Yes it was I have now put it in the right soil.

I agree with what Nancy said. Plant it immediately in bark mix if it is still potted in garden potting soil. Mine arrived in spike and I found another growth in low bud this morning.

Definitely have it potted in bark. It probably was stressed by the dirt and decided to drop that leaf. It should recover once in the right soil.

Is that plant in spike?

as far as I can tell no it isn't in spike

That plant looks close to blooming size. Should bloom soon!