Question about WS2812 strip and FastLED.

Question about WS2812 strip and FastLED.
I’m driving a strip of WS2812 LEDs (5m @96/m, 480 LEDs) with a Teensy 3.1. With a short data wire, the 3.3V output drives the LEDs just fine. I’ve also tested this with a TeensyLC.
The LEDs are powered by 2 10 gauge wires that run parallel to the strip and feed power at each end and every meter along the way. The lowest voltage at any LED is at the far end @ 4.6V.
At full power the strip only draws 16A (16A/480LEDs = 33mA).
it should be drawing at least 21 (45mA each based on some testing) and based on the WS2812 spec (60mA max per LED; 28A)
In my setup, I have

When I select the white and brightness I set.
Set all LEDs to white
fill_solid(leds, 480, 0xFFFFFF)
then of course…;

Am I missing something that would throttle brightness?