Rig with rx580 cards rebooting cant find out why

ok this doesnt make sense to me . my rig reboots after a few min 2- 3 uptime . if i remove one of the 8 cards it works fine . if i use the one card and run with the one card it works
when i tre 7 out of 8 cards it works . but when i try to run 8 cards it starts rebooting . i cant see what is causing the issue . watchdog is off . is there a way to see what making it reboot power supply is 1000 wath for the bourd and risers and 1200 what for gpus . i have 6 other rigs built same way no issues .