My friend group

So i have this friend group that randomly had two members(M and A) spilt, some context, i moved to my new school from Missouri this school year, and didn't have any friends until my bestie D invited me to eat lunch with her friend group. they welcomed me, but i could tell they really didn't want to be my friend, but after a while they got used to me and we all became friends. okay so this group drama started when this new girl(k) started to eat lunch with us, the problem is M's boyfriend used to have a crush on K, and my theory is that m left the group because of that, but i don't know really. the reason while A left is because she and M are BFF so i guess she left to support M. I just don't know what i should do like should i ask M what's up or is that my place?