I believe one of my Sikkimensis, had Calcium and Boron Deficiency, The leaves were emerging with dead tips, thickened veins, and smaller. I ground up some drywall gypsum, and made a liquid solution to water with. Then I took some boric acid roach killer, about 1 gram to one gallon, in a sprayer and spray every other day. The new leaf is emerging much better. Kind of strange since my yard is full of limestone, and chalk?