African Violet~dark edges.
I have had three different African Violet plants where an outer edge small spot of a leaf starts turning dark brownish/almost black, and spreads inward on the leaf. These plants have not been in the sun or in the cold. Humidity in our house stays about 35%. I have had these plants since early summer under 5000 lume lights about 10 hours per day at app 12 in from the light. One of the plants also has what looks like a cut and discoloration around it.
I have caught some very small gnats on yellow sticky paper in the area.
Marion County Oregon
Thank you for your question, Carla. Generally, brown leaves, beginning along the margin, is a water problem. There are some other factors which impact African violets that may be contributing to this, including humidity, which are covered in this Extension article: https://ag.purdue.edu/hla/pubs/HO/HO-10.pdf I cannot tell what has caused the 'cut,' but, once plant tissue is breached, a variety of bacterial and fungal diseases can enter the plant. Fungus gnats are attracted to moisture in soil, and their control is discussed here: https://extension.colostate.edu/topic-areas/insects/fungus-gnats-as-houseplant-and-indoor-pests-5-584/ I hope this is helpful. Good luck!
Boy, Carla, they do not look like the two most common insect pests of African violets: mealybugs and cyclamen mites (which you cannot see with the naked eye). You might want to submit them to the OSU Insect ID clinic, whose information is contained here: http://sites.science.oregonstate.edu/bpp/insect_clinic/services.htm
Sorry. Good luck!