380W measured by the OS and miner software or at the wall? You might be surprised with a much higher value when measured at the wall. Those of us running AMD cards really have this issue.
The safest answer is adding another power supply and chaining them together to allow the use PCI cables for both GPU’s and for the Risers which can pull 75W by spec.
If you are risking molex cable runs with (2) risers, anticipate having a large enough gauge wiring for 2x75W runs to account for PCI specs.
Good luck.