Hi there.. this looks like interveinal chlorosis of the leaves (it turns yellow, but the veins stay green). This usually isn't the case with normal nitrogen deficiencies, but is more of a magnesium, manganese, molybdenum or iron deficiency symptom. If iron deficiency, then the young leaves would show it from the stem outwards, but here it looks like all have it from the outside inwards, so would rule out iron. A magnesium deficiency often goes paired with rusty spots, so my best guess would be manganese.
happy growing!