Size of tank in gallons or litres.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.
It sounds in a bad way and dosn\t sound like it will make it.
Does it look like its fitting.
Have any of your fish gone thin or bloated.
What does it look like when they go the toilet.
Check the anus of the fish to see if its enlarged or red and inflamed.
Check the gills over to see if there pale with excess mucas or red and inflamed.