Doesn't look like scale rot to me. Looks like exactly what you said, dried scales. If she is in shed, you need to bump the humidity up to 70-80% and/or give her a humid hide. I keep my BP around 70ish humidity 24/7. 50% is too low and I would even say 60% is pretty low. Also scale rot is generally on the belly from being kept on wet substrate for too long.
50% is too low when not in shed?? I keep mine between 50% and 60%. High humidity when not in shed and for a long time, can cause an RI.