Q.Why is my poinsettia shriveling?
My red poinsettia are shriveling. They are in a well lit room. They have been watered.
Perhaps they have been too-well watered. If you were to water them every day, for instance, they would get root rot and start to brown, shrivel, and probably die. Do not water again if the soil has water dripping out if you pinch some of the soil between your fingers. Wait until a pinch of soil will stick together when you stop pinching, but fall apart when you touch it. This article has more information: https://www.gardeningknowhow.com/ornamental/flowers/poinsettia/poinsettia-care-how-do-you-take-care-of-poinsettias.htm