Your Calathea Ornata is beautiful!

Water might be the issue. Here are a couple of thoughts.

Most like to be moist but not soggy. If new leaves emerge discolored, then there is definitely a watering problem. You should make sure that the dish underneath is drained so it is not sitting in any water. Also make sure you are watering evenly, and that you don’t overwater....there should be an inch or so of dry soil on top before watering again.

While it is true that Calatheas grow in humid regions, they can do well in low humidity as long as the watering is carefully monitored. Misting raises humidity only as long as you can see water droplets on the leaves. To substantially increase humidity, you would have to mist hourly all day long and that is not practical. Humidifiers and pebble trays are more effective than misting.

Your concern about tap water is also an issue for some. Calatheas can be extra sensitive to tap water, which can burn the leaves. Try using distilled, rain or filtered water, or allow your water to sit out overnight before watering.