Certified GKH Gardening Expert
To me it looks like one of two things. It could either be a watering issue, or too much light.
These prefer filtered light, and not too much of it. Also it is best to water them, only, from the bottom tray.
Here is an article for more information: https://www.gardeningknowhow.com/houseplants/african-violet/african-violet-care.htm