two things come to mind:
1. did you add corn sugar at any time other than bottling?
2. acetylaldehyde - is an off flavor/aroma that's similar to green apples, and is produced by stressed yeast (like low pitch rates, poor aeration, wrong pitching temp, wrong fermentation temp)
how long in primary? did you do a secondary? (i'm guessing you did not since its a wit)
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10