If they are pooping a lot it means they are probably getting more food than they need .
Hmmm how can I explain this.... Basically the poop is waste, unneeded products. So if there is a lot of poop they are getting more than their requirements.
If the poop is runny however, it could be a bad reaction to the food. Bad reactions add gas to the poop giving the illusion there is more poop.
Basically, if you feed 2 cups per day you should see no more than 2 cups coming out, but it should be less.