i have one that is consistently slower than the other ones.
i haven't adjusted anything, should i try for the core or memory? im running them at speed 796.

Definitely should tinker all of them.
You have 35%-40% HW error rate !!! ( HW are hardware errors) ... your miners are actually working only 60 - 65% capacity)
I'm keeping HW under 3%.
EDIT: Read the OP. There is guide how to test them (using --benchmark flag).
the hw rate on minera is calculated by accepted vs error. its not accurate. im running on a solo pool with very high worker diff.. so the accepted will be a low number compare to hwe
in bfgminer log its only 1.5%
[2018-09-27 19:24:18] 20s:34.65 avg:34.79 u:33.88 Mh/s | A:64840 R:230+0(.35%) HW:40689/1.5%
ive tried speed 756 and 768 and it still is the same.