Recent fish deaths...

[George]

Not sure if you want to find out the cause of the fish death or questioning the health of live stock in the fish store.
To find out the cause of the fish death, we probably need to know how they died. Did they have any visible wounds, marks, lumps, dots, etc? Were they eating before they die? Did they die in quarantine tank or display tank? Did they all die more or less the same time or over a few days?
The live stock in that fish store are healthy (or not healthy) similar to other LFS I guess. They don't do any thing special to quarantine their fish. My observation is that health of their more sensitive fish will deteriorate if the fish stay in their tanks for longer time (like more than a couple weeks).