I think only 1 LED need to be replaced check each LED with 3V and 500 Ohm resistor, you don't have to remove them from PCB.
https://www.instructables.com/Simple-Basic-LED-Circuit-How-to-Use-LEDs/
Post # 21, last two pictures suggest that you applied, 110/220 V to LCD board, since they are connected in series there is chance that only 1 is burn out.