other girl calling him daddy

So my boyfriend uses kik. I don't use kik bc that's literally the nude sending app. But he is apart of these group chats with a bunch of girls. I trust him 100% but it's literally only girls which is just weird I think. So today he was texting these two girls in a group chat and one of  the girls in a joking way said "I miss you daddy" and it took me a second to think about it I wanted to be mad or not. I'm kinda pissed not like mad mad but that's just not cool. And he said "you better not try and be mad" so I'm gonna really let him have it he's getting cursed out real good tonight.