That is an interesting observation. Fish that all turn at the same time and look like a precision drill team are the real schoolers. Many livebearers kind of hang out together. That is called shoaling. However several people have noticed a difference between the two species (or if you think they are the same) or "species" in how they shoal.

Poeser, Kempkes and Isbrucker have named the Endler's livebearer, or Campoma guppy as it is also known, as Poecilia wingei in a paper in the journal Contributions to Zoology. They placed both  P. wingei and P. reticulatus (the guppy) in the Poecilia subgenus Acanthophacelus.

The describers based part of the case for the new species on behavior. That is something aquarists are more likely to do than taxonomists. Poeser and Kempkes noted that a male wingei will stay with several females and youngsters in the same schoal. The male (or males?) will mate with the females and then not leave them.

Several on GL have mentioned how fry tolerant the Endler's are. Well fed guppies themselves are a lot more tolerant of fry than some other Poeciliids are (like Gambusia affinis), but cannibalism certainly is known ampng some guppies.

I'm sure there is some movement between wingei groups. But that is quite different from male guppies who are definitely into 3 minute stands. They don't interact any more with that female until the next time they are interested in procreative activity. "What's your sign?" "A fish." "That'll do."

I'm sorry I misunderstood which fish were with whom in your tanks. Glad the Endler's females are not with the Gambusia. It is time to start a sponge filter in an established aquarium. :)