I assume he's really struggling to hit major league off speed stuff. I know when Gunnar and Volpe of the Yankees were promoted (early 2023 for Gunnar), both really struggled to hit much other than fastballs. Fast forward to this year and both those players are mentioned as possible MVPs. You're not going to see a good major league changeup unless you're in the major leagues or a pitcher is on rehab. I would keep Jackson up here but have him sit every 3rd game or so. Offense can sustain it now. I would give him at least a month. If he doesn't improve by early May, send him back down. A week is not really a fair trial. Even great hitters struggle mightily over a week, putting up a 1 for 25 or something similar.