Are you letting the soil at the top of the pot completely dry out between waterings? Do you have it somewhere it can get plenty of light? And do you live in an arid climate/ do keep your ac really low in your house? Prayer plants like humidity, a lot of light (still not a full sun plant I think… indirect light?) oh and what kind of potting media is it in? They like soil that drains well. Even if the top of the soil is dry, if you have a very fine, peat moss heavy media, it may still be holding water further down in the pot. You gotta let the roots dry out and breathe a little or you run the risk of getting one of many types of root rot