Ok how about the bag of food, is it a recently open bag or been open for several months? If it's been open a while the food may have gone a bit stale, and this can put hedgehogs off eating it. If it's a brand new bag and his eatig habits have changed since starting a new bag, perhaps the formula has changed and this is putting him off it.
So how is his heating and lighting schedule? Like I said before it could be either of these two things if they aren't consistent.