in the mid to late 70's i raised bins of red wrigglers. the adult size was about 3". when i had my commercial hatchery i would receive from a local worm farmer 10lbs of red wrigglers a week to feed to the discus fish i bred, they also were about 2 1/2-3" and robust.
the only red wrigglers i can find today and are like the ones in my 5 bins reach about 2"max. are they being inbred so much they have become weak and stunted? they are reproducing, the info today says 2+ in each egg capsul, it use to be more like twenty to a capsul.
i feed very little newspaper or cardboard to them. the type of food determines the nutritional value of the castings. guys marketing worms say feed newspaper. it makes selling worms a whole lot easier then telling people to go out and collect manure and organic waste. but there are studies to show the difference in casting quality.
what size are the worms that you have in your bins?