More bitter a few days later

I brewed an Old Chub clone and when I force carbonated it and sampled it, it was perfect.  Now, a week later it seems less malty and has a noticible rise in bitterness.  Not enough to ruin it, but I like the maltiness of Scotch ales.

Any idea why maltiness (sweetness) dropped off a little and the bitterness popped up a little?

Maybe it was just the carbonation level came up in the beer after chilling longer, and that cause you to loose some of the malt (body)? Not sure, try pouring a glass and let it warm a little and let some of the Co dissipate. 

This is my experience when a beer is too cold.  I don't get the malt but do get the bitter. 

Cold crashing in itself does not precipitate out large amounts of residual sugar or bitter.  Some loss can occur but should not be that noticeable that soon.  I can't think of anything other than than the already mentioned cold and carbonation level.

Cheers!