Original Sour Diesel Auto by FastBuds

It looks like early stage cal-mag deficiency. I would try increasing it and see if that helps the issue. If that doesn't help over a week, keep in mind that ph issues or other nutrients, and even environmental conditions can affect how a plant uptakes cal-mag. So with no improvement I would confirm ph and other factors to make sure parameters are where they should be. Its a little different for me growing in coco, but at least once my cal-mag issue was actually a ph pen calibration issue. Happy growing! 👍🌱