staining

I have these darker stains (very faint though) on the ceiling of my kitchen and living room. The ceiling is not wet, my roof is only a year old. I just recently noticed these stains because they are faint. Went into the attic, took the moisture temp of the wooden beams, and nothing reads above...

I tried my hand at staining a concrete floor recently. Grinding the floor down went great. I purchased a solid color stain (which went on much like paint and not a stain- and therein lies my problem) when I should have known better because the type of look I was going for was that marbled stain...