Why did my dalmation molly die?

She was fine last night was eating and swimming like normal. I woke up this morning and she wasn t very active An hour or two later she was on the bottom of the tank dead. I took her body put to examine her. There was a light brown smudge on her side. Had a golden tinge to it. What is this?
Answers

noselessman

You cant judge by what she looks like now. Did you make a recent water change? is the temp stable? are the other fish ok? what are the results of tests for Ammonia, nitrite, nitrate and ph?

Anonymous

Dead fish look like dead fish. More important info is what you did in the last week with the tank