Screen backlight after water damage LG G2

I have a LG G2 Phone. December 06 2015 I dropped it into water. It was a detergent water in my bathroom. I kept phone for drying for 2 days and used vacuum to take out water remaining. Everything was working fine except some flickering in the screen brightness. The phone worked well until February when I started noticing that if in increase the brightness beyond 70%, the brightness goes dim. It come back after sometime but I need to keep the brightness level below 70% everytime. This time its been a month the brightness is not going up and its hard to see it in daylight. Everything else is fine. I opened the phone and cleaned it too. Even if i keep phone on auto brightness or move the slider manually the brightness is not going up. Yesterday suddenly the brightness was there like 30% it stayed for 1 minute and again the phone was dark. What is the issue?