I wonder if the mattress was truly new...
Some unethical, shady mattress companies have been known to simply re-cover used mattresses. Very illegal.
I wouldn't be comfortable continuing to use a mattress that was doing that.
And we've never had a mattress or cover do anything like that. Black stuff doesn't just appear out of nowhere. Even when I was growing up in an area in which you couldn't hang stuff out to dry lest it need to be washed again from the airborn soot (until I was in Junior High and the Clean Air laws were enforced), we didn't have that happening with the mattresses.
Some unethical, shady mattress companies have been known to simply re-cover used mattresses. Very illegal.
I wouldn't be comfortable continuing to use a mattress that was doing that.
And we've never had a mattress or cover do anything like that. Black stuff doesn't just appear out of nowhere. Even when I was growing up in an area in which you couldn't hang stuff out to dry lest it need to be washed again from the airborn soot (until I was in Junior High and the Clean Air laws were enforced), we didn't have that happening with the mattresses.