Port forwarding to internal router

Hello All,

I need your ideas for my predicament
forum-needsolution.jpg
I simply want to bypass the first router and forward to the second router where my servers are connected to.

RouterA is doing load balancing
Router B is doing distribution and firewall

If you create NAT rules, the traffic will be forwarded.
If you want all traffic to be forwarded, create a very generic rule. Otherwise specify port numbers
/ip firewall nat
add chain=dstnat action=dst-nat in-interface= to-address=10.10.10.51