OK, I think what you are trying to say is that 2.0amps at 123.9V is coming into the controller from the solar array, and the Outback controller is transforming it to 4.7 charging amps at 54.0V? Is that correct? That sounds like the bank is at float, or approximately full charge.
With 320W panels, I would guess that you have them wired 4S3P, or perhaps 3S4P? I would guestimate that each string would be putting out 8-9amps at noon, so only 2.0amps suggests that the controller thinks the battery is full. Alternatively, it might be that some of your connections are bad and only one solar string is functional.
How are the solar strings connected to the controller? Is there a combiner box? I would start out be checking each string individually to see if each one is putting out power. Secondly, I'd try to determine the maximal output the combined strings are actually making. You could do this at noon by putting a heavy load in the system, like a toaster oven. As you switch on the toaster oven, I would think that immediately the amps coming in would jump up from 2A to ~12-13A. If it does not, then the power is not getting into the controller.
If you can confirm that power is coming in from the solar arrays, and that the charge controller has the correct charge settings, then I think the conclusion would be that the batteries are going bad?