Casting two (different) movies from same device to two different Chromecasts.

Here is my use case: I have a plex pass account and have recently added a secondary user (kids) that only displays Kids media such as kids movies and kids shows etc. I used to be able to use my iphone/Android tablet to cast a kids movie to the kids room TV. Then disconnect and cast whatever movie My wife and I wanted to watch to the living room. This no longer works though. Any thoughts?