You might be feeding too much...do they eat some then go back for more, then spit it out? If so, there stomachs are full but their mind is weak. They would rather overeat than risk not being fed again for a long time, so they sometimes won't stop.
Also, the only other thing I can think and have seen before is that if they are really small and you are feeding larger pieces, then they could be breaking it into smaller pieces to eat.
Be glad that they ae hungry and desire eating. This is a good thing. Most of the problems come when they are uninterested in their food.