It’s a micronutrient deficiency the only one ( in reality there are many micronutrients but let's leave them out and consider them one since 99% of the time it resolves with calmag) but u have also a little bit of salt accumulation in the soil, so stop giving nutrient , u have to give them after 3 times water everytime
Meantime buy the calmag biobizz that is wonderful and add some of it, in tap water i would recommend u 1ml/L, 2 only for recovery deficiency, for regular feeding i will not go over 1ml/l with tap water ✌️🏽😊