MK83 / MR80 how to drop or delete an attached device

So I'm trying to move some things around in the network from the main one to the guest network.  but I can't find a way to drop or delete the device from the routers iOS app or the routers web page.  I have a couple of things that have horrible app's so I can't do it from there.  they have no setting for me to make them forget the networks that they have  connected to.  One of them I was able to add to the guest network. but it keeps jumpin back and fwd to the main network. 

Thanks