With the exception of Whittier and Pasadena, I remember when no one would have even considered living in the other areas.
So... prices in affluent areas are tending to drop, while prices in 'less-desirable' areas are rising. Sounds like a bit of migration to more 'affordable' areas of living from people who got in too deep in the pricier ZIP codes.
A year ago, I betcha there wasn't an affluent ZIP code with dropping median prices (in SoCal).