What are you feeding?
What are your RH/Temps at your canopy?
Have you been feeding it with a high bloom nute?
Are you giving it any "N" of the 'NPK'....
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They are not that far gone... You have a couple of weeks to go...
IMO: Not nute burn...
Combo issue- RH a little low at canopy level [the area between lights and top of flower...]
caused your buds to dry a bit...
Also it is my guess that you have not fed with any N in the NPK ratios...
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So, what did you change a week ago, or what happened 7-10 days ago?