Luminosity has drop after water in ...(

Hi all and tks in advance ,

After a fishing day ,i drop my samsung galaxy note3 in water ,10 feet ,after 20 minutes in water i was able to catch it ,but my friend as soon try to power on (bad idea i presume)and he told me that all was ok zzzzzzz

Anyway, real soon ,i unplug the battery ,the sim card and put all that inside a box full of rice for 36 hours

After i try it ,charge the battery but screen was strange and become black in and out ,so i remove all the screw (12)and put the main board in the rice for24hours

For 2 days ,it was ok ,some strange stuff but not a big deal

But later ,the luminosity was not good ,like not 100%but arround 35-40 so the picture is not clear like before even if all is at the maximum on the set up and no picture saving is at on

So i haVE remove again the screw and reput the board inside the rice ,

Question is ,where can i check on the board to see if there is some corrosion ,or what can i do ,to get backmy great cell with great picture like before