Black mold(?) on OSB of outside wall behind tub...

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Kitchener, ON
Good morning,

My project is moving... Slowly :)
finally I ripped out all 30-years old drywall with tiles around bathtub (it was dark grey color with GYPSUM marking at the back) and the rest of the bathroom plus all pink insulation (man it was itchy!!!).

So now I discovered black areas (mold-?) on OSB board for outside wall behind back side of the tub (opposite to showerhead).

My question is: should I tread that areas somehow? I know that vapor barrier was installed incorrectly - only down to the tub (and not behind it). Plus water from the tub wasn't helping too.

I'm planning on living in this house for next 30 years so I want to make it right. I will put new Roxul insulation and proper vapor barrier all the way down to the floor with ANOTHER layer down to tub's lip.

But what about this black areas?...



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Hey, wait a minute.

This is awkward, but...

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