Older large fan leaves turning slightly pale but not serious yet

https://dutch-passion.com/en/blog/a-visual-guide-to-cannabis-deficiencies-n987

Center yellowing on new development is usually iron/manganese deficiency while the spots is calcium deficiency at its early stages. There might also be a case of heat stress. Your light is a bit too close to the canopy. try going for minimum 20 inches. Something like 24 works well

From my observation maybe there is signs of heat stress? Taco style leaves could be heat stress, clawing could be over watering. Is the light really close? Too much light intensity causes a high use of cal mag. Be careful just adding cal mag thinking it will fix it. Other issues can show through looking like cal mag issue. Make sure there’s no lock outs and don’t make a big change at once or the ph will for sure get jacked up. I’m not a professional and this is just from my perspective. Take everyone’s advice with a grain of salt

If the spotting ( small yellow rusty spots) are only on the larger leaves. And predomanently on the lower leaves. Yes, this is low calcium. Because your leaves still appear to have a nice dark green huw to them I'd stay away from a cal-mag mixture. Your plant doesn't show signs of a magnesium problem. The issue with calmag mixes, is they over do it with the magnesium, and under do it with the calcium. A question of material costs I guess? Seeing as you're going organic. I'd recommend that you google or youtube "how to make calmag"...it will cost you peanuts and you will never want to go back to retail calmag again. I've made mine using eggshells and epsom salt... You're cathing this just at the right time. cheers, GC

la foto della foglia è un inizio di carenza di calcio ma è comunque minimo bastano 3 o 4 correzioni e sei apposto normalmente avviene sulle due foglie opposte