I am constantly amazed at the number of plant doctors there are. First we don't know how long this person has been flowering, what growing medium they are in, what feeding schedule or what they are using and no pics. So far here we have people saying N def. or maybe too much, heat stress and other things.
Post pics of your grow and some background to your grow then someone could make an educated guess, right now you have people they you what might be a problem. As reggaerian said Don't listen to anyone until you have posted the info on your grow and we have a chance to look over your situation, trying to guess on multiple problems and you listening and trying multiple remedies at the same time is a sure fired way to damage your plants further.