I know I'm late but if we could rank who is the most fluent in mandarin to the least it would be: Kun, Hnedery, Xiaojun> Yangyang> WInwin> Lucas> Ten . I think it's a tie for Kun, Hendery & Xiaojun. (Lucas is fluent in Cantonese, Winwin fluent in Wenzhou dialect, Yangyang grew up in Germany, so they, including Ten had to learn Mandarin)