I can't quite tell from the photo if what I'm seeing is powdery mildew or possibly damage from a change in culture such as a change in sunlight or watering.* Powdery mildew is a whitish/grayish frosty-like dusting on the foliage, blossoms and flower stems.* Does the discoloration rub off?
This site shows many different leaf problems that African violets experience.* Anything look like what you are seeing?
Have you looked at the underside of the leaves to see if there are any bugs?
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.