Which molly are you concerned about?
It looks like a female black molly has clamped fins and this is usually caused by poor water quality and stress.
One picture shows a black male with some white spots on its body. Is that colouration on the fish or something new and what you are concerned about?
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The biggest problem with mollies in aquariums is soft water and water with a pH below 7.0. Mollies need a GH (general hardness) of 250ppm +, and a pH above 7.0.
What is the GH and pH of your tank water?