I am no expert and by all accounts seems like your temps ,humidity,ph, are all inline ,I guarantee if you post this plant on auto infirmary for sick plants you will get a response within a day by an expert,there's this dude waira he knows his stuff ,others also I had a problem not that long ago an posted on there got help AFN is the best ,I wish I could help and I am very curious also to the problem,I am always trying to learn more,can't learn enuff at least bro we are in the right place.