Chromis odd behavior question

So I got 5 blue/green chromis today and have them in my quarantine tank. I acclimated them over a couple hour period. They've been in the QT for about 2 hours now. 4 of them are fine and swimming around together but one is sitting at the bottom and he swims around and ate some frozen food. He starts to swim up but then falls like a rock, its almost like his swim bladder isn't working. Any thoughts? I'm hoping it is just some adjustment issue but given how differently he acts from the others I am skeptical of his prognosis.

 

Yeah he is breathing really fast compared to the others. He doesn't appear to have any signs of disease on his outside such as velvet, ich, or uronema. He is swimming around a little more now, but still labored in movement. I'll check first thing in the morning. I almost want to yank him out now but all thats in my QT is the other Chromis so I'll give him a chance.

 

Well he bit the dust. All the others are doing great. I guess he must have been injured somehow in transport or just got too stressed.