The information you have provided is not enough to do a good review of your system. However, this may not be necessary. I don't know how long of time those fish were in the bag -- that is how long does it take to 'get them home.' Assuming a reasonable trip of less than 2 hours, I'd say the problem is with the fish.
Chromis is one of those fishes that are not very 'important' to the system. They are found in the wild in great numbers and thus do not have much of a value. Add to this that they are not also in high demand. The catcher, holder, exporter, importer, wholesaler, and then the LFS are not that into making a big effort to handle them properly. The mortality on these fishes can be greater than 70%. The catcher gets about $.05 each and the LFS pays about $.25 to $.50 each for them.
Where did you acquire these fish? How long did the source have these fish?