Soaking can help, are you having rough sheds too? I don't have issues with humidity and still have the same, maybe they could be a bit dehydrated, I just don't know. The patches is likely that they are coiling the same way and not in perfect circles at least in my case for sure and they seem to appear at the bends. I am quite sure it isn't a problem just a curiosity.

On a side note for humidity issues I also have a dry house 12% in winter. I use a handful of methods to keep it up in the enclosures. Hanging wet laundry in the snake room is a great way to get the humidity up! I use coco coir (eco earth) and it holds tons and releases slowly. Also terracotta hides (flowerpot trays work well) will adsorb water if soaked and they increase it locally. I have also used sandstone rocks soaked to help too. Just tossing out some ideas...