I've had my Emcomm box closed with the radios mounted in the chassis inside a Spuds7 box.  I noticed that the steel screws have a little white haze on them.  Should I look more into this on the inside of my radios, power supply, tuner, and Signalink?  The box has been sealed for at least 5-6 months.
The box was in contact with my basement floor. My plan in the future is to keep it off the concrete floor and not keep the lid closed on the gasket or at least keep a Humisorb Desiccant pack inside.
Has anyone run into something similar to this?

Are there batteries in that box also?

No batteries are in the box.  I planned to make a separate box dedicated just for batteries.

The screws probably contain tin which is crystallizing and becoming tin whiskers.

Sounds like galvanic corrosion. All you need is dissimilar metals in contact with one another and enough humidity. 

https://en.wikipedia.org/wiki/Galvanic_corrosion

Maybe wipe them down with some rem oil or something.

Keep everything off basement floors!  Plastic tends to wick moisture from concrete.