Female black and white tegu trying to mate w female

[Wicrain76]

Hi everyone, I have several tegus. 1.1 black and white Argentine. 1.1 red Argentine 0.1 blue tegu. At what age does a female start producing infertile eggs. I have not bred mine yet but my one female tries to mate with my other female when around each other. It started this week. I am keeping them completely separated during free roaming now so they don't hurt each other. What are some things to watch for.