That kids can blossom and they can regress and they can remain constant. Is that change purely genetic? Is it chemical? Is it environmental? Does nurturing matter? Why not?
Consider this observation. There are families that are able to discipline their children to practice music. Other families fail to discipline their kids to develop music talent. Even when the parents say they want their children to have music talent, the practice doesn't happen. Is this outcome because of the kid or because the parents themselves lacked the prerequisite discipline?