Same subnet or different for wifi devices roaming between offices

I have an office with 4 floors and 4 separate networks, all running their own separate DCHP servers.

All of these networks have the same Guest Wifi SSID allowing people to move up and down as needed.

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Does it make any difference if they are all on the same subnet or should I do a different subnet per network?

Thanks for any tips, I have the wifi working well but want to check I have the networks setup correctly.