Any chance of a picture of the fish?
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.
What are the tank dimensions (length x width x height)?
What is the GH (general hardness) and pH of your water supply. This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
What symptoms are the fish showing?
How long has the tank been set up for?
How long have you had the fish for?
How often do you do water changes and how much do you change?
Do you gravel clean the tank when you do a water change?
Do you dechlorinate the new water before adding it to the tank?
What sort of filter do you have?
How often and how do you clean the filter?
Have you added anything to the tank in the 2 weeks before this started?
