Hello. DWC system. Some kind of deficiency symptom...

Hello. DWC system. Some kind of deficiency symptoms have appeared on the lower leaves. What could this be? pH 5.8 Tap water: 0.3 EC + CalMag Agent 0.15 + Canna Aqua Vega A+B 0.85 = total EC 1.3 Water temperature: 25 °C VPD: 1.3 Thanks.