I doubt it would be that one stick slowing the system - but for future reference do not mix RAM suppliers if you can help it - they do not 'normally' work well together.
they are all the same speed which does help

so they will all run at the maximum speed - MOBO permitting.
I would check the RAM manufacturers and see what there timings are they will probably be 4-4-4-12 but have a look and check that yours in the BIOS correspond -
I would guess that the CORSAIR and KINGSTON RAM needs more juice to get them to better timings but you will have to check the Micron one can handle it.
you may get better performance with just the 2 sticks of Kingston and run them at the sites recommended timings and voltage
