Whats wrong

To me it looks like more of a Potassium (K) deficiency which is more likely than Calcium deficiency since it shows more signs of deficiency at the bottom of the plant than the top (Calcium is immobile in the plant which means deficiencies or toxicities will appear on new growth/ top of the plant first) Potassium deficiency - Leaves yellow from the bottom of the plant to the top, lower parts started showing signs of chlorosis and blotching. Try increasing your Potassium uptake with increasing the PK/Bloom solution you are using by 50% and check after a day or two for improvement. if deficiency persists then increase by another 25% Hope this helps! Good luck and happy growing :)

@Roberts i water with a ph of 6.2-6.5 every time

Also make sure ph is correct. Your nute levels might be right but locked out due to off ph. 20 percent run off each feed is a good amount to was out prior salts from chemicals

You are cal mag deficient. If growing in coco coir you need to up the amount a lot. Coco absorbs calcium. Cannabis has a big window with how much calcium it can intake. I have experienced this before as well. Happy growing

Generally, rust-colored spots on marijuana leaves indicate a fungal infection or a deficiency in magnesium or calcium. Nutrient burn is also a possible culprit. 🤘😤