Have you looked at your municipal water quality report? Just wondering if there's some weirdness there. You might try using a different water source. But yes, you are exhibiting some nute burn AND some lock out at the same time. That almost suggests that there's a pH problem. Are you sure you can trust your pH meter? Have you tried liquid drops or test strips as a second opinion?
That said, if your pH is fine, then it's probably overwatering. But since you're using hempy buckets, that's kind of odd. It makes me wonder if maybe the perlite you used in the mix was too fine? Extra coarse perlite is the best thing to add to vermiculite for a hempy mix, in my experience. When the perlite is too fine (particles too small), such as the kind that Scott's sells, it can actually cause compacting and drainage issues.