Hi All! Thanks for your many helpful suggestions and ideas. We live in the RV full time and have been doing so since 2011. I can only hope and pray that there is no leakage from the roof. What a PITA that would be. I am pursuing this as though it is an excessive moisture/humidity issue. We have found the mold on the other slide out as well, although nowhere near as bad as what I posted up in picture. We have also found mold in the bottom cupboards, under the desk, of the small office slide. We have been running the dehumidifier daily now and I am checking the cupboard interior for moisture daily as well.
We also found mold in the window slide rails of several of the windows which leads to me to believe again that the moisture is humidity related and not a roof leak. Regardless, we will be monitoring the situation with hyper vigilance until we get it figured out.
Further thoughts and suggestions are gratefully accepted. Thanks for reading!
Cheers!
Mike and Carol