Yellow leaf, possibly virus?

[the yuk event]

Hello there,

I have an Angraecum Sesquipedale, and one of the leaves has slowly been turning yellow and less stiff than the rest of the plant. Initially I believed that this was due to over-watering, so I cut back on how often I watered it. However, the yellow seems to have spread further into the leaf and I'm worried that soon the entire leaf will be in danger and possibly the plant itself. It's a very young plant. Any ideas? Thank you.

- Justin