So I had Deco M9 network of 2 nodes 

I now upgraded to XE75 Pro (3 nodes)

Upon setup (replace main eeco) my deco M9 just started to blink red light, so I instead of adding device to network, created new network with XE75 only. I use same network name and same wifi name/pass.

While devices work well, I want to add my tp-Link DDNs to this network, but it says my hostname is already in use. Which is on the previous deco M9

How can I transfer that to-link DDNS to new network?