I think that’s normal. Kids pick a language they feel most comfortable with. We spoke nothing but English at home so our kids reply in English but interestingly they speak Japanese between each other. I remember when I came to US, I switched over to English and even though my mom would speak to me in our native language I always responded in English because I was more comfortable with it. To this day she tried to speak to me in our language and I still respond in English 🤣