Indoor gardening apps aren't likely to be very accurate, as many factors can cause overlapping symptoms like leaf die-off or yellowing. Your photo didn't come through for some reason (you're welcome to try sending it again with your reply), but Calathea plants are known for being a bit picky about their environmental conditions as a houseplant. They prefer moderate to high humidity, which is difficult to achieve indoors in winter with dry ambient air (a humidifier might help), and they want to be somewhat evenly moist without staying too wet or getting too dry between waterings. Their leaves naturally move a bit between daytime and nighttime, but any leaf that stays wilted and discolored (yellow or browning) is senescing (preparing to fall off) and can be clipped off.

We do not recommend watering any plants on a set schedule; they should always be checked to make sure they actually need to be watered instead. Their moisture needs will vary throughout the year, and as they age and their roots fill more of the pot. How quickly a potting mix dries out also depends on its ingredients, so there is no one set watering schedule. The general guideline is to feel the potting mix and let it get somewhat dry to the touch about an inch down before watering, and make sure any water collected by a saucer under the pot is emptied after any excess water drains, so the pot doesn't sit in water and re-absorb more than it needs (which could drown roots).

Miri