The bigger crappies I've caught been deeper then the smaller ones when they're in schools( daytime fishing ).In the summer I usally find them on their own little piece of structure ( stick,stump,ect.) away from all the little ones on a big piece.I think it's so they don't have to compete for the food.I have my own little slot limit on crappies and release all my big crappies so there will be some to catch down the road.It could be on your lakes in the years past to many big ones were keepted and now they have gotten genetically smaller.Just a thought.
:D Give a man a crappie you feed him for a day...teach a man to fish for crappie and get rid of him for the weekend!!!