Test for too much or too little water by poking your finger into the soil about one inch. Then your limp impatiens are about to get fungus and die. Stop watering immediately. Test daily with your finger and you may save your flowers by backing off the water. Fungus appears often with impatiens in pots and impatiens with mulch.
Pots can easily be over watered.
Add some rainy days and all can die. Mulch holds water. With over watering or a period of ongoing rains, mulch can kill impatiens by providing an environment for fungus. It is common sense to know plants need food and water. You should too, but be careful to not over feed with strong liquid fertilizers.