If you can find these kinds of 750 Ti’s, it may be possible. This can send up to 75W of power through PCIe. But you might be hit with bandwidth limitations, PCIe Gen2 NVM it Supports PCI Express (PCIe 1.1).
Else try getting
Molex to 6 pin(but seems like 1 of the 2 molex is occupied)
Another possibility is SATA to 6-pin (which is not possible since all are occupied).