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If you mean the very dark dots on the lower fin in the pic, I think those are just the way they are colored.
here is a bad pic but you can kinda see the same thing in the tail, if that is what you are talking about, this ones are a little longer and not just kinda dots
If they are regularly spaced and / or in the same part of the fin, like in between the rays or bones I think it is fine. Yours fins look healthy and smooth, not diseased.