Money tree leaves - nasty looking!

This is a newish plant, which I got as a present last August. It's in a very light bathroom on an east facing window sill behind partly obscured glass. It's been growing well up until now. Any ideas as to what I'm looking at here?  I'd hate to lose it this plant.




Most leaves are find but a few look like this



These i took off - they were near the centre of the plant.