Hey there SweetSpot, you've got the start of a magnesium deficiency, you can tell from the yellowing between the veins of the the oldest leafs first . If it gets worse you'll see the sides of the leafs start to discolor and burn. Nothing easier to fix : just add cal mag to the feed and consider making a foliar spray with cal mag and fish mix and spraying that twice a week. Do this and the problem should stop spreading within a few days and the plant should completely recover within 10 days. Basically some plants just have phenos that eat more mag or it could be that using two different additives (root juice and fish mix) is simply a bit too much for this more sensitive pheno . Hope this helps ! 🚀