Stargate Atlantis

So, I am watching season 4 of Atlantis and I got to the episode where they wipe out the nano replicators by sinking their collective masses into the core of the planet to initiate a massive explosion. Earlier in the episode, they show one of the rebel replicators, in the same form as the female doctor on Atlantis, explaining to the team of captors that they indeed were not captors but were built in a lab by nanites to the specifications of the real Atlantis team who had visited a while ago. During this explanation, she talks about how the other replicators aren't in agreement with these rebels' goal, which is to find out how to ascend. A bit later, when the other replicators find the rebels, she tells the new nanite-built Rodney that they don't have enough ZPMs to power the city's shield, because they could not get their hands on enough of them without raising suspicion. Are we supposed to believe that the replicators can build entire Ancestor warships, and entire replicas of Atlantis, and replicas of living people, but they can't manage to replicate a ZPM? That is the biggest and most ridiculous plot error in Atlantis so far. The replicators could have built millions of ZPMs if they wanted to.