Hey , what kind of heat source do you have in your home ? going from 70 percent to 20 percent in a couple of weeks sounds like you have way to much air extraction and dry air heat source,like a wood stove and a dehumidifier blasting away .? Baseboard heat is very dry as well .
Boil water for tea , make a nice homemade soup from stock ,double down on you boiled potatoes ...get some moisture back in the air .
It`s not rocket science ,,,perhaps it is lol If you heat with wood ,have a kettle on it , good luck .