The other key sign of carrydown is when the ball starts to push a couple feet further, but still retains an angular look when it finally moves.  I agree that burnout is more common than carrydown, but on flatter tournament patterns carrydown can be a major factor in the early transitions.  Carrydown usually manifests itself by the middle of the first game.  If you are seeing the ball stop hooking after a couple of games or more, it is probably the heads causing the rotational energy to burn off early. 

If the heads are going, I would definitely go to urethane or a really tame resin ball and try to stay outside on a shorter pattern.  On longer patterns, I would keep moving in trying to find some head oil and would look to pearls that will hit hard without having to hook a bunch.