Only thing I can think of is ..... you may not be in deep enough water
Some might suggest that your baits weren't big enough, or you weren't going fast enough, but I've caught Crappie that size Pushing jigs at 1-1.5mph & on cranks (Bandit 300's) at 1.8mph ... so that argument is +/- moot.
I say you may not be in deep enough water, because at a local lake I've been catching keepers & barely keepers at 8' deep in 15-20fow, while other members fishing the same lake have been catching good sized keepers fishing 15' deep in 20-30fow (though they are fishing a different section of the lake than I am).