We would suggest that you contact Holtkamp Greenhouses Inc., the largest producer of African violets in the world. They are a private company based our of Nashville. Suffice it say, it’s a multi-million dollar business.

According to the African Violet Society, plastic pots are preferred by growers. Clay pots allow too much evaporation adn the soil will go dry at the top, probably because the moisture is evaporating out the sides. Select pots which were designed with rolled edges. That said, there are times when a clay pot is desirable– most especially in hot climates or greenhouse growing. The evaporation from the clay works as a cooling device and actually keeps the roots cooler. Since many growers are in climate-controlled environments, this feature seems to be less important these days.

It’s normal for violets to grow with a tight crown that spreads out over time, but it sounds like your plants’ new growth could be stunted, which would cause a “traffic jam” of sorts in the center of the plant. Stunted growth can be caused by a number of things, but because you’ve tried adjusting your care in multiple ways already, you may want to try treating the plants for pests, specifically cyclamen mites. Cyclamen mites are tiny, nearly-invisible mites that attack new growth and can cause stunted growth if their numbers get out of control. Other symptoms of mites include grayish leaves and twisted leaves in the center of the plant.

First, you should isolate the affected plants away from other plants, then try a few rounds of treatment with an insecticidal soap spray, which you can find in most garden or hardware stores. Make sure it’s meant for mites and other houseplant pests. Before you treat the whole plant, try the pesticide on a leaf or two, then wait about a day to make sure that there is no adverse reaction. 

It sounds like you could be describing mealybugs or spider mites. Spider mites create thin webbing on the plant, while mealybugs look like tiny white, cottony spots. In either case, the first thing you should do is separate the infected plant away from others and check the plants around it for signs of the pest. They like to hang out on the undersides on leaves and in the center of the plant, where they feed on new growth. They both spread by crawling from plant to plant, so ensure that the infected plant is sufficiently far from other houseplants.

The pests can be wiped off or squished with a paper towel (or your fingers), but there are likely more than just the ones you are seeing. Try treating the plant with horticultural soap or neem oil. These can be bought at most garden centers or hardware stores, and are organic pesticides. It’s important to test the pesticide on a single leaf and wait 24 hours before using it on the rest of the plant, just to make sure that the plant won’t react negatively to it. 

If this doesn’t improve the situation, you may need to dispose of the plant, unfortunately. But preventing a larger infestation should be the #1 priority!

It’s not necessary to remove the old leaf, but in theory you could use the same leaf again if you carefully separated it from the new plant. Depending on how young the new plant is, the old leaf may still be supporting it, so it would be wise to wait until the new plant is well rooted and is big enough to sustain itself. 

We can’t explain the “growth like thing”—at least sight unseen. However, wet leaves or too much water can lead to the brown-edged leaves and softness you describe. It may be that the soil is not draining. The African Violet Society (linked above) may have more detail about these specific conditions here on its “101” pages: http://www.avsa.org/learning