That looks like a tumor I cant be exact but it might be lymphocystis--a viral disease with no known cure.
Also 8 mollies in a 15 gallon tank is too many most go with the theory of a 1 inch fish per 1 gallon of water mollies get to be between 3 and 5 inches.
Another note you can rotate the picture by opening it theres 2 arrows under the pic as well as zoom options 1 that goes left 1 that goes right just hit
one of the arrows til the picture is turned upright to desired position. (If you use windows that is)
Also 8 mollies in a 15 gallon tank is too many most go with the theory of a 1 inch fish per 1 gallon of water mollies get to be between 3 and 5 inches.
Another note you can rotate the picture by opening it theres 2 arrows under the pic as well as zoom options 1 that goes left 1 that goes right just hit
one of the arrows til the picture is turned upright to desired position. (If you use windows that is)