Yellow Spots

pH problem most likely

Personally I do not think this is a calcium issue and it is definitely not septoria, but to me it looks like the start of burning due to over feeding. Acapulco Gold, being a Sativa dominant plant, requires lighter feeding than your average hybrid, so the chart you are using is too much. Having grown this strain, half to two thirds strength nutrients is plenty for this strain.

Based on what I can see, the yellow spotting and mottling on the fan leaves (especially the older ones) suggests early signs of a nutrient imbalance or stress, which is fairly common during mid-to-late flowering. A few possible causes stand out: 🌿 Most Likely Causes -Calcium or Magnesium Deficiency (Cal-Mag) -Yellow or light-colored spots appearing between leaf veins. -Often appears mid-to-late in flower when demand is high. -Common if using RO/distilled water or coco/hydro without supplementing. -Light Burn / Heat Stress -Upper leaves closest to the light can get pale/yellow spots or edges. -Leaves may curl slightly upwards. -Nutrient Lockout / Salt Buildup Following a feeding schedule can sometimes lead to salt accumulation, raising root-zone EC and blocking uptake of Ca, Mg, Fe, or Zn. Especially possible late in flower when the plant drinks less. ⚡ What You Can Do -Check pH of your nutrient solution and runoff (soil: 6.2–6.8 / coco: 5.8–6.2). Off pH can cause nutrient lockout. -Flush with plain, pH-balanced water if EC or ppm runoff is high — this clears salt buildup. -Supplement with Cal-Mag (if not already included in your Advanced Nutrients line). -Inspect leaves for pests (thrips or spider mites can sometimes cause similar speckling, but your photos don’t strongly suggest this — just check undersides to be sure). Adjust lights if they’re very close — back them off a bit or increase airflow to reduce heat stress. Some leaf yellowing is normal in late flowering as the plant cannibalizes older fan leaves, but spotting is not normal senescence. Try to correct the issue gently — large nutrient swings or overfeeding late in flower can do more harm than good. Hope that helps. 😘

Oh, now u thinks it,s Ca ? Well, this time u guessed right. Congrats 1 of 10 times 😝

Would say calcium or ph fluctations if indoors, but outdoors it can be beginning of septoria