Strange Marks On Molly

[jameshughes1989]

Woke up this morning to find my male silver molly with four strange dark lines on the side of his body. They are on both sides. Nothing like i have ever seen before. He also has a black lining on the tip of his tale. Haven't got a pic as cant get one with enough detail.
Could this be fin rot?

Any help would be great as im confused.
Cheers

 

[saz326]

sounds like a burn to me. Maybe chemical - maybe heat.

Is the heater protected?

 

[WILDER]

How many gallons or litres is the tank.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.

Does the heater have a guard.
Black patches can be ammonia burns that are healing.