Maplegirl...I don't know if you resolved your Calathea problem or not, I just noticed your thread.

Cals love humidity. Humidifers work best, (for most plants) but misting and humidity trays help a lot, too.

I allow soil to dry a bit between waterings, especially in winter. Never keep soil soaking wet. And don't overpot..in fact, Calatheas do much better in smaller containers.

Stick your finger in the soil..if it comes out wet, don't water..if it comes out dry, (similar to baking a cake) give it a drink.
They like bright light but no direct sun..since you're in Canada, a south or west window will be sufficient (in winter) They don't like heat aiming at them, (artificial heat) so keep out of the way of a heating vent, etc.
Good luck, Toni

Hi Maple girl
( good nom de plume ) the other thing that Calathea's like is warmth ,no not direct heat as it dehydrates the foliage ,but they are decidedly tropical ,Zebrina is the hardiest but is it the purple backed form ,or the white backed form or the form with the gold zigzag across its leaves ( looks like lightning flashes ) the purple backed form is the toughest,as Tony said ,moist not wet ,feed well,and yes not to big a pot ,all at time will go dormant if to cold for to long ,but they will come up in spring ,if the leaves also go dry and brown looking than the air is to dry ,humidity is a must. Cheers ,Jack