settle down now just let your plant live it will be fine you are half way there all the sativas ive ever grown did the same thing just like indicas they do it to it just happens
if it starts at the bottom of the plant and on the outer edges and tips its just useing up excess nitrogen that it does not need as it is getting close to bulk up and ripening time you dnt need such a harsh nute either during flower, your feedin a lot of n that it does not need right now its trying to finish it up how long you got left on it 5 weeks get some pics up when ya can