This looks like you may have spilled something on it, if it’s just that one spot. If not then it’s a form of the Mosaic virus is my guess. I’ve grown a Deiselberry one time that had Mosiac, it probably lost a 1/3 of the plant before it just stopped. I would remove that stem but I would also wait for a second opinion. I am just guessing. Some strains are more prone to it than others, sucks Brutha
Hope you accidentally spilled something.