Hey Growmie,
After taking a look at your diary this could be the result of a few things, the first would be the ph, it's too low for the plant since it's flowering, at this stage of the plant's life you should try to shoot for a ph of 6.0-6.3. Another thing that can cause this is too many nutrients in the growing medium, I know you said you haven't gave it any nutrients but for some reason the plant is showing signs of too much nitrogen, when this happens the extra nitrogen burns the roots causing the fan leaves to become extremely dark green and crispy. Hopefully, this was helpful, and remember ... "Happy Growing" and "Free your mind one puff at a time".