I have some gorgeous white impatiens that were doing wonderful, now all of a sudden the leaves are turning yellow and they also have dark spots on them. They are planted in the ground. Does anyone have a helpful hint? Thanks so much.
Either the soil got too dry, or the soil got too wet. The black spots are .. well "black spot" .. a disease which can seriously defoliage the plants. It sounds to me that the soil got too dry (this is how our impatiens look if the leaves turn yellow and black spots appear).
In future water reguarily, and apply a diluted fertilizer with every 2nd watering. Do not allow soil to become completely dry. They develop large root systems which in pots means that they can get very "overcroweded" as there is not much soil or potting media left. Therefore, if you grow in pots, consider upgrading the pot to a larger size.
I recommend cutting them back to a few healthy leaves and them water regularily with fertilizer every 2nd watering. Do not keep the soil overly saturated (soaked) either as this can lead to root rot.
if they are in pots..make sure they are not root bound, place in larger pot if this happens.