Lemon Tree Punch (Clone)

This is potentially really bad... gently pry somem bud apart between calyxes so you don't cause too much damge. look underneath where leaves are dead. is there any grey or white fuzz there? if so you have an infected plant. throw it out. get it away from the rest of your garden ASAP. leaves will also pull out incredibly easy - can try that first. even so, i'd inspect under the buds along stem anywhere the leaves have died like that. sure it could be nute-related, but such a thing is not sugar-leaf specific, so i'd be worried about disease from this picture.