Are you feeding this lady at all? What you've got is the beginnings of a potassium deficiency... but without information on what you're feeding, what the pH is of any solution you're giving (including water), I can't tell you what you should do about it... so just google "potassium deficiency weed" and you'll come up with lots of pages that will address the problem and provide solutions... GrowWeedEasy is a good site for this...
Good luck!