While it is true that Calatheas benefit from high humidity, low humidity can be compensated for by proper watering. It looks like you repotted your Calathea and that can make watering more problematic depending on how much bigger the pot is, the porosity of the soil you used and whether the pot has drain holes.
Ordinarily, a Calathea will need water as soon as the top half-inch of soil dries. However, if you repotted and added soil to the top surface, then that equation no longer applies. In any case, it should get dry enough to need water about once per week.
Indoors in winter, it is hard to give a Calthea too much light. Keep it on or close to a sunny windowsill at least for the next several months.
Finally, leaf damage such as yours has can also be a sign of excess mineral salts in the water if your tap water is hard or if you are over fertilizing. Use distilled or filtered water if your tap water is hard. Stop fertilizing if you have been.
