Rig working few hours,and then one of gpu lose mhs..example 55mhs to 0 mhs..and show like gpu is dead..!! I check risers one by one works well..stock gpu work some period and again on 0 mhs..undervoltage as well ..if i put 4 of them..then works without problem..
This happens when you either overclock or undervolt too much. Try dialing it back a bit on the GPU that is failing.