I have been using this app for 2 years and just found out today that my Calathea is sensitive to lime in water. It was purchased from a nursery last year and was so beautiful. Slowly it started having dried up and curled leaves. I kept treating it with a fungicide, watering and fertilizing on schedule. It finally got down to one leaf and I almost threw it away, but I kept watering and feeding. Lo, and behold it started growing again and the leaves are big. I see the dreaded dry and curled leaf starting again and believe it’s lime from the water. John, my plant, will be getting distilled water from now on.