J.G.
They go through phases. We had a clingy phase right around 20 months with my twins. Usually they would switch off, Max one day, Harry the next, sometimes both. Laying on the floor sobbing, "mama". I would come back to look at them through the window after taking my daughter to her room and they're laughing and playing. They're there together and have been going to the same place since they were 16 weeks old. It last maybe 2 weeks??? They also pick up on what other kids do so if there's a new kid that's never been to daycare and those parents come back in the room cause the new kids is crying the twins figure "hey, that's how I get her to come back...":0)
Good luck!
Jenny