Led on arduino UNO dim while in delay ?

Hello,
Can someone tell me why my led’s on my UNO are dim while the millis delay function is active. I am a beginner! The code works like I want it to but for some reason the led’s go dim while the countdown is active. I’m supposing something in my code is incorrect. I am using pull-down resistors on my breadboard.

byte sensorOne = 2;
byte feedOne = 8;
byte augerOne = 16;

unsigned long feedEmptyMillis; // when feed level dropped below sensor
unsigned long turnOnDelay = 3000; // wait to turn on auger
unsigned long turnOffDelay = 10000; // turn off auger after this time

void setup() {
  // put your setup code here, to run once:

  pinMode (sensorOne, INPUT);
  pinMode (feedOne, OUTPUT);
  pinMode (augerOne, OUTPUT);
}

void loop() {


  unsigned long currentMillis = millis();

  boolean prox1 = digitalRead (sensorOne);


  if (prox1 == LOW)
  {
    digitalWrite (feedOne, LOW);
    digitalWrite(augerOne, HIGH);
  }

  if (prox1 == HIGH)
  
    feedEmptyMillis = currentMillis;
  
  if (currentMillis - feedEmptyMillis <= turnOnDelay)
  {

    digitalWrite (augerOne, LOW);
  }

  if (currentMillis - feedEmptyMillis <= turnOffDelay)
  {
    digitalWrite (feedOne, HIGH);
  }
}

Which LEDs are you concerned about ?

Ok my LED's are the augerOne and the feedOne outputs.

Because you switch them on and off at a high speed

  if (prox1 == LOW)
  {
    digitalWrite (feedOne, LOW);
    digitalWrite(augerOne, HIGH);
  }

  ...
  ...
  if (currentMillis - feedEmptyMillis <= turnOnDelay)
  {

    digitalWrite (augerOne, LOW);
  }
  ...
  ...

As long as prox equals low the second if results in true, augerOne goes HIGH / LOW all the time. Same for feedOne.