It seems as if you crossed a vCore limit - not memory.
In Yarn Queue Manager what calculator are you using ? Default or Dominant ? If Dominant - swithc to Default.
In Ambari >>> Yarn >>> Configs >>> Settings - make sure CPU Scheduling & CPU Isolation are off (unless you have switched them on intentionally and you are using cGroups accordingly).
Also in In Ambari >>> Yarn >>> Configs >>> Settings make sure you sufficient "number of virtual cores" & "Maximum Container Size" (it should be the number of cores you have in your datanodes minus 4-6 cores for OS).