Creepy_Steve has nailed it.... it's most likely phosphorus... but I don't see any nute information in your diary or any record of the pH... if you're feeding normal cannabis nutes, they should have sufficient phosphorus in them, at least through the veg state and since you say this has been her color pretty much all through veg, I think the problem might be your pH? If it's below 6.2 or higher than 7.0, the plant won't be able to absorb the phosphorus it needs...
Good luck!