There's no way to tell what is going on... you don't have a diary going on this grow so any advice/opinion is going to be nothing but pure guesswork. Start a diary, join this community and we'll be able to help you MUCH better.
Good luck.
Look like nitrogen deficiency, not much you can do at this point in flowering but next grow you can use veg nuts few weeks more to make such discolaration happen the last two weeks of flowering.