Why is Apex Legends dropping frames during combat?

Intense combat in Apex Legends caused voltage drops to 11.8V-12.0V, throttling my GPU and dropping FPS from 144 to 90. I tried increasing the power supply limit, which caused unexpected reboots and made things worse. I used GamePP Power Plan Switcher to change from Balanced to High Performance and enabled BIOS power management optimization. After a brief stutter, I fine-tuned the parameters. AIDA64 confirmed voltage holding at 11.9-12.0V. RTSS showed frame intervals stabilizing from 12ms to 8ms. Power supply fan speed stayed at 1200 RPM.