Looks like you need a PK boost to me, you're a little early into flower for natural fade which is likely not far off maybe 2 weeks or so away, not often is PH a issue with organic soil, I would give them a PK boost and go from there, not very long from now you're going to see natural fade and you might get worried but that normal, in a month when start to flush you'll see even more so just relax and watch them buds bloom...Good luck