However, the remote airport is not relaying my wifi signal
The A1084 AirPorts do not have a setting to "Extend a wireless network", which is what you need if you want the Express devices to provide more wireless signal coverage.
As it stands, the AirPorts are likely configured to "Join a wireless network". This will allow you to use AirPlay / iTunes...or connect a printer to the USB port on the Express, but the AirPort Express devices cannot provide any additional wireless signal coverage when they are configured to "join" a network.
Can you check to see how the AirPort Express devices are configured?
Thanks for the clarification.
If you connect the first A1392 to your router by Ethernet cable and configure it to "Create a wireless network"......and......locate the second A1392 where it can receive a strong wireless signal from the first 1392.....then the second A1392 can be configured to "Extend a wireless network" to provide more wireless signal coverage in the general area where it is located.
Try to minimize obstructions in the direct signal path between the two Express devices for best results. Ideally, they will have line-of-sight with each other.
The Ethernet ports on the 2nd A1392 will also be enabled, so you can connect an Ethernet device that way if needed.
AirPlay will function as normal, as will the USB ports on the Express devices.