If the pictures are too big for the website, set the camera's resolution to its lowest setting and take some more. The lower resolution will make the images smaller and they should fit on this website. Check the pictures on your pc and find a couple that are clear and show the problem, and post them here. Make sure you turn the camera's resolution back up after you have taken the pics otherwise all your pictures will be small.
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If the fish were freaking out when you first put them in the tank, there is something wrong with the water in the tank. Test your ammonia, nitrite, nitrate and pH levels.
How long was the quarantine tank set up for before the fish were added?
How long were the fish in bags for before you got them into the tank?
What is the pH and GH of the water at the pet shop and your tank?
Contact the shop and see if they will give you a replacement fish. Keep the body in a plastic bag in the freezer and take it with you to the shop so you can prove it died.