Freightliner M2 with Cummins ISC 8.3 uneven idle, won't rev.2

[Gapvalley]

Working on a 2015 Cummins cm2350 driver came in with a miss. Connected insite to truck found a active code 4726 engine fuel leakage not sure if this is my main issue or not. Cutout cylinders found cylinders 1,3,5 are missing. 2,5,6 make the engine change rpm. Pulled the valve cover off and started engine intake and exhaust valve are all moving and Jake rockers are not moving. Next step my be run a valve adjustment if there all within spec maybe ecm. Looking for any input