The painted lines are sometimes baseline suggestion for getting you in the correct-sh range, rather than accurate, precise indicators of where perfect tune happens.
From where the lines indicate the hub should be in tune, try backing off the cable adjuster a couple 1/4 turns and see if that makes a difference. Worse? Go back a couple 1/4 turns to where you started and keep going another couple quarter turns the other way. Check again.
Might not fix the issue, but since it is as simple as it gets before delving further, worth part of your diagnostics routine...
How long have each of these hubs been in service? Over a year, and I'd definitely advocate lubing with a heavy oil.