I purchased 2 tangs from my LFS yesterday they were both in the same tank and doing beyond well in said tank. They’d been quarantined in the store for a month and I had gone to see them a few times this past week deciding on the purchase and every time I went in the tangs and tank looked immaculate. I bring the tangs home and immediate issues. The purple tang is perfect, no problems whatsoever, the royal blue tang on the other hand is suffering and I can’t figure out why. The RBT is laying on the bottom of the quarantine tank (which yes is a metal kitchen bowl for the time being as I was preparing my 20 gal actual quarantine tank for them). The RBT started laying on the bottom of the bag when they were in there at first so I assumed it was just stress. After a day it seems to have only gotten worse as the RBT had lost so much colour (his black stripes looked grey) and when he would try and swim he would swim stomach up. I checked the salinity and it was dangerously low so I added a small amount of water from my QT to their bowl, since doing that the RBT has gained some colouring but hasn’t moved. I’m not sure what to do. I’ll attach photos and videos of both tangs as some help would be greatly appreciated. The RBT has some fin damage but he was shipped to the store like that so I do not believe it to be related. Thanks in advance!