Black Molly died within hours

[frizzlenizzle88]

I just put in my new black mollies 7 hours ago. I got my water tested everything was fine. I let the fish bag adjust tempature before putting the fish in the tank. I come back 6 hours later after putting them in and I notice one of the black mollies is dead. When I put the fish in I noticed this specific fish acting weird only going to the top of the water(not gasping at the top though) and not wanting to eat. When I took the dead molly out to examine its eyes and body I noticed the part on top of his mouth is like cut open. I found this to be really weird. Can anyone tell me what happened and how to prevent the other fish from dying?

 

[emeraldking]

It sounds to me more like an injury than an illness. Maybe it got already hurt at the store. In case of an injury, I wouldn't be worried about the others.