That may be the cause then, I’ve had pretty good luck with shipping in the past but I’m not sure how tangs do with shippingThe problem with dshipped fish is you want a turnover of at least twice the water volume to equalize salinity and PH and fish in shipped bags produce carbon dioxide and ammonia. The carbon dioxide lowers the pH of the water in the bag, That in turn makes the ammonia non-toxic to the fish. When you acclimate them, if not done just right, you drive off the carbon dioxide faster than you are diluting the ammonia. That raises the pH of the water in the bag, and that in turn, makes the residual ammonia toxic to the fish.