Continuity mistake: The aging Kirk's hairline has receded considerably. When he ages still more and goes completely gray, however, the receding process inexplicably reverses itself, and he suddenly has much more hair on his forehead than before. (00:34:35 - 00:43:55)
Continuity mistake: Mr Checkov has a rather unfortunate hair styling during the beginning of his role in Season 2. In this episode his hair is normal until the end, where in between being given an order and carrying it out he somehow manages to go and have his hair professionally done and made all bouffant. (00:47:15)
Continuity mistake: The Romulan vessels fire plasma weapons (as seen in "Balance of Terror"), but when they hit the Enterprise they become photon torpedoes.
Answer: After causing Norman to overload, all of the other androids shut down. The same could be said for the androids on the Enterprise.