Help!!

[KeMo]

update!!

The fish did not make it through the night I feel shitty.
Im almost 100% shure that they sold me a sick fish like someyone said.
Was in their this morning to give them a piece of my mind. Looked in their main display tanks and saw more then 3 fish , 2 with fin rot and one with marine velvet.

I will never be shopping their again. Plus they are still saying that my ph @ 8.0 is what killed him. Fish was dead in less then 48 hrs.
Fin rot had spread to his body. Could that happen ? like could my tank cause the thing to rot away in less then 48 hrs ? everything else is fine in the tank. All crabs,snails,1 clown fish , 3 feather duster , leather corals ?

Thanks for taking time to read all who did .