I have 2 girls right now who are both butting heads and competing for top spot. They are driving me CRAZY!!! They are constantly argueing, telling each other "not to say that" stealing each others toys but not actually playing with them, storming off in a huff, sulking, kicking legs...give me strength.

1 is leaving in 2 weeks so hopefully my group dynamic will settle back down then. I have experienced a few occasions where a group dynamic changes because of one child. I think they feed off each other. Good Luck and at least it's coming to an end soon and only 1 day a week for you.