They are 6-Pin risers. The 6-Pin has a 6-Pin to Sata adapter attached.
It is then powered by a 3-connector SATA power cable, with only 2 of the connectors being used per wore on PCI-E risers.
E.G. 6 GPUs will be used with 3 SATA power cables.
and that is no good. well gray depends on draw. A sata cable can do 75 watts.
So if you have 2 risers and pull 38 watts each you are too hard on the cable.
You are not crazy stupid ie 3 or 4 per cable
You are borderline.
rule of thumb is below
molex 1 = safe ,2 = gray, 3 = wrong , 4 = wtf are you thinking
sata 1 = safe, 2 = gray, 3 = wrong, 4 = wtf are you thinking
pcie 1 = safe ,2 = safe , 3 = gray , 4 = wrong
I have found msi afterburner sometimes drops settings and goes to 100% tdp on 1 card but not the others.
That may have happened to one of your cards. You may have damaged the psu in 1 sata jack.