That’s right, none of them is a native speaker of English - their English is learned via the standard combination of school, extracurricular courses, media exposure, and other typical means available in largely monolingual countries, and subsequently polished up abroad (at least two of them moved to Anglophone countries for university). Thus, I figured that the undercurrent of their native pronunciation should be sufficiently conspicuous to allow for making some educated guesses about their origin 🙂