You might find over the winter months your streptocarpus plant gets a line across the leaves like in this photo. It's nothing to worry about! It's a natural occurance with streptocarpus and it's called an abscission layer.
It's the line created when the plant is responding to a cooler period, the plant takes all the good nutrients from the end of the leaf, creates a line, and then lets the end of the leaf drop off. It's a similar process to deciduous trees losing their leaves in the autumn. When the line becomes really well defined you will be able to snap off the discoloured end section
