Swapping them is the easy way to confirm if one has gone.
I shouldn't think they'll be hard to replace, don't bother trying to reseal them, this is the easiest way to kill off a tired pump!
Would this slow the ram down the longer I use the digger? Logic does say that the oil is thinner when hot, but once it stops raining ill wait till its hot and then swap the pipes over and see what happens and then report my findings,As Bill says don't strip the pumps yet, go through the system logically, start with the bits that control system pressure and flow, the relief valves and DCVs they will have taken some stick in the machines life, it's not unknown for the PRVs to have broken springs that massively reduce the pressure they lift at or leaky seals. Check the DCV linkages are giving full movement on the spool.