Wow no one answered, I would have had I seen it. Iam ahead of you by one week going into my 4th week of flower. I have a shitload of yellow leafs everywhere but not on top. This is the normal process. I have already gotten to the point of no return. You can't add nitrogen it will screw up your buds and the plant will try to go back to veg. Just be patient and keep going. 1/2 way up on most my plant is shedding but I just have to ride it out. Good luck and hang in there!