My time has come

[born]

So my first tank nuke just happened. In my 34G, I had a peacock mantis shrimp and various other fishes+corals.
My mantis wasn't looking too great the last couple days, I thought it was a possible molt or she was dieing. And each day it looked more like death was coming. So one night at work, I get a call saying she looks like shes dead, I get home(1am) and it she was on her side not moving. I was about 99% sure she was gone, but just to kind of finalize things and since I wanted to triple check she had died, I left her in the tank till morning. Around 10am my mom wakes me up to the words " whats wrong with your tank!?" I jump out of bed, and all my fish are dead on the sand. And my peacock mantis shrimp was for sure dead as well.
I took every dead fish/mantis out of the tank. Do a 50% water change on the system, and empty the skimmer, clean any thing I can.
1 birdsnest coral is slowly starting to bleach. my candy canes kind of seem like they're (swollen/puffed/inflated ballon/ like its gonna burst?). zoas kinda closed up a little acans look alright.
Parameters; PH:7.4 Ammonia: 0.5 Nitrite:1 Nitrate:5
water params are messed up.
Im buffing the ph now, is there anything else I can do?
And I was thinking of moving my corals to a friends and cousins tank, but I dont wanna nuke their thanks if I have something toxic in my tank.