Thanks for starting this thread!
I'm going to try all of the above, starting with the Vick's.

:)

Is toe nail fungus what causes your toes to turn yellow?

Fungus can cause nail thickness as well as yellow color.

If you wear toenail polish, when you remove it, you might notice your nails are yellow. Something about the oxygen being blocked from the nail by the polish, I don't really remember (beauty school was a LONG time ago) but you can bleach them back to their normal color. . .