My 5yo keeps saying she wants to live with mommy fulltime now

We were 50/50 for almost 2 years and it's been working fine. But last month my ex apparently told her she had "the most space" at her house and now my daughter is saying she wants to stay there. She literally has the same bedroom at both houses and spends the same amount of time at each. I'm trying not to freak out but this feels like it came out of nowhere. Should I talk to my daughter about it? Talk to my ex? My anxiety is through the roof rn ngl.