I don't know if the OP's coming back but I guess I'll just add my two cents.
From what she said, she repotted them into glass containers, which suggests to me that they have no drainage. African Violets are very sensitive to root rot from overwatering. Sometimes the rosette of leaves hang on while the root (which in normal state is a single fat taproot with side roots) rots away until one day, the entire rosette falls off. She also didn't mention what kind of potting soil she used.
1/2 strength chemical food, even those sold specifically for African violets is too strong in my opinion if used at every watering. 1/4 strength, maybe. Especially in a container with no drainage, there would have been a buildup of fertilizer salts.
She also didn't say how often she was watering, but as several people commented, African violets do better when allowed to dry somewhat between waterings. In fact, they are extremely drought tolerant and easy for beginners who tend to forget to water.
After flowering, they should be allowed to rest for at least a month. Newly purchased plants are usually either IN full bloom or has JUST FINISHED full bloom, so it makes sense that hers needed some rest. During the rest period, they should be watered a little less and only with plain water, preferably filtered or de-chlorinated (I.e. tap water left in open container for 24+ hours to de-gass), or, if you can manage it, with rain water.
Light exposure was explained/elaborated by other members and I agree so I won't belabor the point.
