Impatiens.

Impatiens are beautifull flowers included in Balsaminaceae family. However, they can be infected, especially by Impatiens necrotic spot virus which accounts for most of the virus infections we detect in impatiens. Common symptoms in garden impatiens include dirty-looking, dark-colored rings, black stem sections, distorted leaves, and leaves that drop off.
In order to diagnose the origin of symptoms you can test on your plants, as you will see in this usefull video :

Click on the links below to learn more about Impatiens Nerotic Spot Virus and all the other pathogens that can be detected in Impatiens with our test kits :