the first card its connected on the PCI-E 16x? with riser or no riser? u use windows or linux? u primary video its comming from the gpu or the onboard motherboard video?

maybe some config on u miner can resolve this, equihash for what i know dosent mess up the primary from the secondary card hash rate, use u intensitive -i command to see if change samething, need some time trying to resolve this its normal.