Neon tetras going into shock and dying?

I live in a small area and there is only one place to get fish without traveling at least 70 miles (minus Walmart). I like the little store, but I'm questionable about how they treat their cheaper fish.
today I decided to buy 6 neon tetras to add some color to one of my tanks. When the lady at the fish store went to net the fish, many of them went belly-up. She explained to me that it happened all the time with their neons and Oscars and she thought it was heart attacks. I saw a few of them "come back" after being put back in the tank, so I assumed it was shock. It made me nervous that she kept checking that the fish were alive while I was checking out.
It is a short 8 mile trip home. By the time I got there, one was dead. 15 minutes into floating their bag, two more died! There was no extreme temperature change or any unnecessary shock. one thing I did notice is there was a louse in their bag, and a pretty big one for as small of a fish they are.
I was wondering if they are just that sensitive of a fish that they are dying of stress/shock or if it is more likely a water condition/disease? I wish I would have saved some water to test (ooh and I got the louse off too!)


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Thanks. I'm not sure if they were new stock or not, that is a possibility. I know they've had many neons every time I've been there and they didn't have an exceptional amount this trip. No quarantining. I have them in a 10 gallon tank right now that I just moved some healthy guppy fry from (before adding them, of course.)
Like I said, the ones that died didn't even make it out of the bag. It was strange seeing the ones being netted just instantly dying.
The other three are still alive and seem to be adjusting well. If they survive a week or so I might have to make an hour our so trip to get them a few buddies.

I don't have anything against the lfs and I will purchase from them again, just not neons. It's a little family owned place and they have a lot of stock for the three (all family) staff that runs it. I've gotten many fish from there and they have thrived. Like I also said, it seems they just shrug of their cheaper fish.

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It ended up that two of them died in the night. I found a very small white spot on ones fin, so I'm assuming they aren't healthy and the added stress of being moved was just too much. I expect to lose the last one today. I'll probably add salt to my tank, let it sit empty for a few days, and reintroduce guppy fry for a bit before getting another school because I'm nervous about the louse I found.
the neon tetra look isn't my favorite, my fiancee picked them out.

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