The more you can tell us the better as we just get confused, we can't see your tank from here, so the more you tell us the easy it is to help, since it has a cut on the gill as he been breathing heavily, i would add abit of melafix to stop infection.
What we are trying to say your ph is 7.2 but the stores ph could of been say 6.5 meaning that you would have to climatise them for hours adding water gradually, causing ph shock.
I would ring them and find out, to rule ph shock out. when buying fish that are being shipped test the water in the bag for ph so you no how long to climatise them for.