Minifigure arms and legs do not have stamps
Nope!
Torsos and leg-pieces are special. They are some of the few pieces of their size that are not actually two separate parts of different IDs. Torsos actually include their two arms, which is why they come assembled, with the arms and hands already attached, and only the torso is stamped. Legs are actually a three-piece combo of left, right, and waist. A mini-figure is made of (typically) a hat/hair piece, a head, a torso-combo, and a leg-combo, all of which have only one stamp apiece. So fortunately for you...
All of your pieces are legitimate.