Hi, while replacing my internal SSD and cleaning dust out of my Mid2015 15 Retina Mbp. I observed 2 strange stains on the inside, one on the internals of the magsafe connector and the other one on the other side at the surroungins of a screw .... Strange on the otherwise perfectly clean interior of this mbp. My MBP got never any water damage, was never used or carried in the rain or in humid environment, it sits at my desk since 2 years and has never been moved. See 2 pictures for details. Any idea what that is or could have caused this?