Who were the fish from ? How long had they been out of the hatchery (in truck)? Doubt it is your water but rather stressed fish. Glad they will replace - a good sign.
It could well be how the fish were handled going IN to the truck as well, you just never know for sure.
One other item I've seen in the past is tank cleaning agent that doesn't get properly rinsed from tanks, mainly bleach compounds with the current day concerns of invasive species.
It can happen..
