Think about both src-address and dst-address of packets in both directions.
The RB connected to internet listens on public address. On this RB, you can set a dst-nat rule to translate e.g. dst-port=48291 to to-addresses=first.panel.ip and to-ports=8291, and another one to translate dst-port=58291 to to-addresses=second.panel.ip and to-ports=8291. This will ensure that the packets from the internet will reach the panels' interfaces. The src-address of these packets will remain the real one. So both panels need to have your internet-facing RB's LAN address a default route's gateway. If that is the case and you cannot conect to them from outside, look at firewall rules. If it is not the case and you can change the default route this way, do it. If it is not the case and you cannot change the default route, you'll have to add a src-nat rule to the internet-facing RB, causing the packets towards the panels which come from the internet to be src-nated to the LAN IP of the internet-facing RB.
Instead of writing novels, post /export hide-sensitive. Use find&replace in your favourite text editor to systematically replace all occurrences of each public IP address potentially identifying you by a distinctive pattern such as my.public.ip.1.