Help solve the Mildewed Lemon mystery!!!!!?

Hi! I encountered something I don't understand: I had put 3 large fresh lemons in the bottom drawer of a refrigerator, with temperature adjusted to slightly lower than medium. It's been several weeks. I have a lot of other food in the refrigerator, too, with no problem. Then, today, when I had a good look at the inside the drawer, I saw a roundish thing, COMPLETELY 100% MILDEWED, even the other food nearby caught some mildrewed dark green dusts! I couldn't tell what that round thing was (imagine a green baseball!!!). When I tore it, I found it was one of those 3 lemons!! STRANGELY, both the other lemons are still good, no mildew at all. So how come this single lemon was completely thoroughly mildewed to such degree???