Need to change WiFi. Password remotely

I connect both Rachio 3 and Flow meter on my Wi-Fi router and it’s working so far perfectly okay but I like to change my Rachio 3 to my router extender and I will leave Flow meter on the my Wi-Fi router.
The Flow meter is close to my Wi-Fi router and Rachio 3 it’s a close to my Wi-Fi extender. Both Wi-Fi router and Wi-Fi extender have the same password and almost same name except that my Wi-Fi extender have on the end dos name EXT like example MyNetworkName_2GEXT and the my Wi-Fi router have it just MyNetworkName_2G.
If I connect Rachio 3 to my Wi-Fi extender and Flow meter on the WiFi router it’s this going to be some kind of problem I mean they will be able to communicate and property work like right now when is connect just on the router