Screen Dims when connected via display port

[Mcguckind]

Hi,

Im running os10.15.3 with an RX 570 4GB graphics card
when I connect my 27 inch 4k Dell monitor Via HDMI, then great
But when I Connect Via the Display Port, the screen periodically goes very dim, which makes Logic and Final cut very difficult

I need to use 2 monitors, but my 2nd is a 21inch 1920 x 1080 and only has an HDMI interface

Hope you can help
Kind Regards
David

 

[theruck]

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