I’d talk to your manager about it, but focus on your feelings of exclusion rather than proposing any specific solutions. It’s certainly natural to feel what you’re feeling.
But I’d also recognize that an “English only” policy is also going to have downsides for your team. At the very least the member who’s struggling in English will be put into a similar position to you, but it might also lead to the other Mandarin members just talking less altogether.
There are also things you can do to help foster communication. Even if you’re a fluent speaker of a language, group discussions can be challenging - often by the time you’ve formulated your thoughts it’s already moved on. One on one communication is much easier, so you could go out of your way to make opportunities for it. Pair programming, for instance, can work even when your pair isn’t a fluent speaker.