Q.new Guinea impatiens
Leaves turning dry and crumbling.
Two things came to mind. Your impatiens may be getting too much sun and/or not enough water. Have you been keeping the soil moist? New Guinea impatiens do not tolerate drought very well.
For more information on new guinea impatiens, please visit the following link:
https://www.gardeningknowhow.com/ornamental/flowers/impatiens/new-guinea-impatiens.htm
For more information on impatiens problems, please visit the following link:
https://www.gardeningknowhow.com/ornamental/flowers/impatiens/impatiens-problems.htm