[woeh]

I've used a cheap hygrometer last winter, during which the air inside my home was always way too dry. I had to place humidifiers (with some success). The difference in humidity for inside and outside temperatures is huge. You can calculate the relative humidity for different temperatures with online calculators such as [0].

Long story short; if you still heat your home, but some degrees lower than you used to do, you are probably fine regarding mould.

[0] https://www.omnicalculator.com/physics/relative-humidity