Relay not working properly with nodemcu

Other Hardware 3rd Party Boards
39 
const byte K1 = D6;
const byte K2 = D7;
const byte K3 = D8;

void setup() 
{
  pinMode(K1,OUTPUT);
  pinMode(K2,OUTPUT);
  pinMode(K3,OUTPUT);
  Serial.begin(9600);
  Serial.print ("led is ready");
}

void loop() 
{
  digitalWrite(K1, HIGH);
  delay(500);
  digitalWrite(K1, LOW);
  delay(500);
  digitalWrite(K2, HIGH);
  delay(500);
  digitalWrite(K2, LOW);
  delay(500); 
  digitalWrite(K3, HIGH);
  delay(500);
  digitalWrite(K3, LOW);
  delay(500);
}