Those flare marks are caused by the adjacent caps that are filtering vcc_main and the nand power rail. That tells me that this is where the water shorted the vcc-main line first.
As @oldturkey03 says, the shields have to come off followed by a proper microscope inspection. Then a bath, rinse and dry. Only then can you start probing and trying to determine what the issue is. Many water damaged phones can be saved if they were attended to quickly and professionally. Just because some shops wont touch them doesn't mean they should all be trashed. Despite the poor quality of the images, this one doesn't look that bad to date, there isn't even any corrosion on the connectors.