The first you can try its to clean board with isopropyl liquid even without ultrasonic cleaner. Usually the first where damage from water is the display PMU (U1501) or backlight IC's (U1502&U1580) because high voltage. If board cleaning not give solution you need some skills and knowledge to find out if some of those chips are damaged.
Did you unplug the battery during the LCD replace? If not probably backlight filters damaged. (usually FL4211) To check if filters damaged plug lcd and boot the phone. Drop some light above screen and try to see the apple icon. If appears so filters damaged.