I am not sure what the topology is based on the posts here. I think you have an upstream router with at least the default gateway for one subnet.
And now you have added a second to that upstream router?
Plus you have RVI on the ex to allow the 3? subnets here to communicate with each other?
So from a routing view the upstream router has direct routes for those two networks and would need a route added to reach the 3rd via a route to the RVI on the ex for one of these configured subnets. Then potentially then share that route wiht other upstream devices on the nework so that subnet has reachability.
On the ex you would create the RVI for all three subnets to communicate. And add a default route to one of the upstream router addresses to reach the rest of the network.