Possibly cpu can’t cope with running 4 at that speed, I would run them all at 4266 and tighten the timing a bit maybe 18 18 18 39, the memory is working fine at 4400 in a2 and b2 so the memory isn’t the issue, some cpu can’t run all 4 at full speed as the memory controller can’t cope with it, you will normally find you can get faster running speeds when only using two sticks. To be honest you won’t really notice much difference between 4266 and 4400, glad you have it all running thou and bet you are seeing some solid FPS increases across the board