g0at, I totally agree with Ryllharu on the point that the diclonius you saw in the episodes were not Lucy. They were 2nd generation diclonius, as referenced to in the episodes. In earlier episodes, they mentioned that many diclonius were killed and experimented on. This episode is just showing that situation.

Nana was number 7, and they have, as far as we know, at least 35. As mentioned in the episode, the limitation of the facilities was the main reason why they started killing off the newborn diclonius, meaning there were already multiple diclonius in captivity.

Also, I just want to mention again that any of the diclonius could infect/seed people, so the infected people's newborn becomes diclonius. That was what happened to Kurama.

Stoopider, I agree that there seems to be some sort of mutation, but it is the third generation (non-directly from Lucy), that are different. Nana has a longer reach, and number 35 has twenty-six arms. The first generations were probably similar to Lucy, except they lacked the ability to reproduce themselves.

Eurasian, they focused on the other diclonius probably to show that it was a widespread situation, that it is happening all over Japan, and it wasn't all Lucy's doing.