One thing i have noticed is that most of the fish being caught shallow, like where I can reach them, are black crappie. The black crappie move up sooner than the whites. Also the white crappie out number that blacks 10:1 or so. I would get more concern when water temps drop in the mid to lower 50's and still not seeing the white crappie. Not saying that you are wrong, it could very well be an issue, but think it is too early to tell yet.