rhdsilvi85

ok so im confused.. I rewired my car with jdm wiring because I had some issues with some stuff... on my old car I had an issue with voltage dropping between the two taillights.. I used a volt checker and with my battery being low (12.2volts) at the back rhd driver tail lights it was 11.8v and at the rhd pass side it was 11.3v.. can anyone shed some light on this? also does anyone know what would cause my brake light to work and then stop working? the light on driver works but pass doesn't any tips on how to test? tried to change bulb but that didn't work..