OK, I have now fixed the problem, which was a bad configuration on my part. I didn´t deleted the post because it might help someone in the future…
The bad configuration on my part is that I didnt restart the 2:de PSU (powering 5 of the cards) before I started the 1:st PSU that is powering the Mobo/cpu and the 3 cards.
Now when I am doing everything in the right sequence, everything is working fine!