are you waiting for top 1" to dry before watering? if not, try that and see how it responds. Since it stalled, dial back on nutes a second, too. if you are adding ferts to a pot where aplant isn't drinking much, it could build up more easily.
treating them the same is great at first, but anytime a plant starts reacting differently, you have to react to that plant individually. Even clones can have some oddities no matter how hard we try to make everything the same.