using CCminer under linux 4.12.4, Nvidia drivers 384.59

One card shows 456 MH/s, the other shows only 379 MH/s while mining LYBR (but I do have this problem with any other coin), both cards are Galax EXOC 1080TI, both connected directly to the motherboard, no raisers. No overclocking on any, no SLI, the only difference is that one of them is connected to a monitor right now, the other is not.

Any tips on how to approach this?