Zendaya Good Genes or Good Docs TMZ

Barbara Palvin is getting real with her fans about a health struggle she's kept private -- revealing she recently underwent surgery for endometriosis after years of painful, debilitating periods.

Hilary Duff says her new album is her finally being ready to share who she is ... including her "very complicated" family dynamic and beef with her sister Haylie.

The Rock's daughter, Ava, can say whatever she wants now that she's left WWE ... and her first free words were quite liberal indeed ... and directed straight at Donald…