Simpler would have been to change
int LED[] = {5};
to
int LED = 5;
and change:
for(int i=0; i<ledCnt; i++)
digitalWrite(LED[i], LOW);
if(tag > 0 && tag <= ledCnt)
digitalWrite(LED[tag-1], HIGH);
delay(5000);
digitalWrite(LED[tag-1], LOW);
to:
digitalWrite(LED, LOW);
if(tag > 0 && tag <= ledCnt)
digitalWrite(LED, HIGH);
delay(5000);
digitalWrite(LED, LOW);