Hi Celeste,
Nice looking guppies there, well done with them.
Essantially your guppies are turning into wildtype guppies which are smaller in general. Fancy guppies are selectively bred for colour, fin shape but also for size. That's why most if not all fancy guppy strains are larger than wild type guppies.
As for your question:
Guppy is Poecilia reticulata
Endler is Poecilia wingei
Basically you cannot create a different species by selectively breeding. Once you have a hybrid you can not get back to a pure species through selective breeding either. What you have is some nice looking wild type guppies, which are very interesting in their own way.
Hope this helps a little. If you are ever in Canberra, I can give you some pure endlers for free.