Precision 3580 4k screens

I have 2x new Precision 3580 laptops and have just bought 2x 4k screens for both but only one works correctly at 4k the other would sit at 1920 res max. I then realised the docks weren't correct so replaced them with the WD19DCS which uses 2 USB-C ports and are rated for 2x 4k screens but I still can only use one screen at 4k. The only thing I notice with the USB-Cs is only one lights up the other doesn't.  In the bios I've set the power from 7.5 to 15 but this doesn't make a difference also turned off discrete graphics.  In Windows the monitors are set to use the inbuild Intel graphics driver not the NVidia and I can't find an option to force them to use the NVidia, If I disable the Intel, they just use Microsoft basic driver and not the NVidia.  Both monitors are using 4k rated Display Port cables.
So a little stuck now if anyone has any guidance please.