Begonia problem - Fungus?
 

Hello,

I bought a begonia basket from Tesco flowers for mother's day (only because it came with a free spa treatment).

Went it arrived it was looking healthy.
The plant has been sitting alone on a shelf, in a well ventilated area near a window.
I noticed a couple of weeks in that the leaves were looking strange but, there wasn't anything visible eating it. Now it is very unhappy and has a white powdery substance all over it.

Anyone know what it is?
Do you think the plant was already infected when I bought it?

I've took a couple of photos, but I don't think it's showing up.

http://i102.photobucket.com/albums/m...e/Begonia1.jpg
http://i102.photobucket.com/albums/m...e/Begonia2.jpg

Thanks,
-Kate