7 fish; 4 guppies and 3 mollies. 8 small live plants and 4 artificial plants. Water is clear. Temperature is between 75-80 degrees Fahrenheit, ph is 7.5-8.2 all other parameters are fine. The Cremecicle Lyretail Molly is female the only problem is tiny black dots near tail. Disease?
Are you sure it isn't color variations as it ages? Can't see much in that photo. Is its behavior still normal. Exact ammonia/nitrite/nitrate readings? What may be fine may be an issue to others or an insight to others.