Brown blight on Tea Plant

Hi all! First post - eek!

I've been growing a tea plant (Camellia Sinensis) for about 6 months indoors by a window.  I noticed it has managed to get brown blight which is a weak fungus infection that turns the leaves brown.  I wondered whether anyone knows how to get rid of it? 

The plant itself is fine and is still growing with many leafs unaffected however it's a real annoyance to see random leafs turning brown! I've balanced the soil PH to be a little more acidic and keep feeding it plant food so as I say, it's growing strong - does anyone know how to actually get rid of the blight? 

thanks!