How often are you watering? You may be over watering it or is it in
direct sunlight for extended periods of time now that the weather is warmer?
African Violets tend to like being slightly pot bound but if yours is
still in the original soil it was bought in you should try repotting it.
One of mine grew much healthier after I repotted it into some new soil
and out of its original soil. When you repot it observe the roots and if
they appear brown and maybe even scarce or look like they were dying back
that is a sure sign of a root pathogen. In that case cut off on the
water a bit. One other thing, are you watering from above with cold
water? That can cause necrosis on the leaf surface.