Blätter hart, kräuseln sich , CalMag wird gegeben, nicht so stabil wie die restlichen, bleibt in Position wenn man sich drückt/biegt, Blätter rau

Hello! It does not look like a calmag deficiency, it looks like a viral infection I experience every now and then with some of my plants, especially in countries with climate like yours. I strongly advice to remove the plant from the grow. I do not think this is a light related stress. Please note that too much calcium can lead to nutrient absorption deficiency. Maybe reduce watering for a week, give the substrate the chance to dry for a few days.