O2 issues

maizenblue

Alright, so I have a 2010 Z 65k miles. Back in january the fuel pump died. At the time it was already throwing codes p2a00 and p2a03 for both upstream sensors. I figured the pump was the issue and replaced it but the light never went away.
Fast forward to february when my fender liner falls off and my car sucks up water. I live in the north so salt is everywhere. Salt coats the filters and maf sensors. I just replaced the filters and maf sensors on Thursday, as well as a clogged up pcv valve and spark plugs while I was at it.
now, the car is throwing codes or both downstream o2 sensors. All I can think of is that the salt killed them but why is it just now popping up? Im not sure if I should just replace all four sensors or what?