Buds Drying Up And Dying On The Branch

Hey Everyone,
 
I wanted to see if anyone can help me out or if anyone has experienced a similar problem. 
 
About 4 weeks into flowering some of the lower buds started drying out/ hardening off and dying on the branch. This slowly spread up the plant. Some plants were virtually all destroyed by harvest time, on some about half the buds were salvageable. Others somewhere in between. The buds that survived looked amazing.....good crystal formation and tight, dense nugs. 
 
My next round is showing evidence of the same problem and trying to decide how to treat them. In veg and early flower, the of the fan leave curl up from the sides of the leaves, not the pointed ends. I will try to get a picture of that as well. 
 
Here are a few pictures from the recent harvest. Hope you all can see on here. The tops of the buds look great, dense and crystally. The bottoms are hard, dead and lack any crystal structure. 
 
Any thoughts/ experience/ advice would be very appreciated. 
 
Thanks! 

 

The strain is great white shark. Doing them on 4x4 hydro trays, fill and drain set up. They are in 3 gallon coco pots.

Done many rounds of the same strain in the same location with same set up, nutrients, etc.

Humidity was higher then normal this summer, rectified that. Also, had lots of miller moths this year. They made their way into the garden. Didnt seem to do any harm but they would end up in reservoirs, pots, etc.

Thanks!