That 0.1 volts makes a difference to the modules at the end of the rack.
For sure you should turn the voltage up a bit. You can go as high as 5.2, but no higher.
Some docs to help; http://documents.opto22.com/1271_Tech_Note_Using_Power_Supplies.pdf
Longish post about UPS’s and rack power supplies in the Forums; Opto 22 SNAP PAC power supply and UPS recommendations