Why isn't it going away?

New growth looks green, but you are talking about a mobile nutrient. it's getting worse because the entirity is in a steady decline for weeks. if what you are adding hasn't been working, it likely is not the cause. I may be symptoms of a mg or ca deficiency, but it could have been caused by pH or a p and/or k toxicity too. just a high EC/tds also. Back off on ferts for a few irrigations. you are in soil. it'll be okay. let it runoff, though. You are five weeks in, so i wouldn't flush for long, and don't over do it... just want to dilute what is in your soil a good bit... then resume with a low concentration of a well-balanced feed. if you need to add things "this week" or "that week" it's a bad feeding schedule / system. at worst, you should dial a few things up or down out of a very minimal number of products that you put into your soil/soilless or reservoir - equally apply to all.