0k so this is my first grow and my leaves started getting like these rust like spots on them. I'm around 4 weeks flowering.and some leaves are curling up.you guys got any idea on what this is ive looked it up and i think its calcium deficiency just wanted a second opinion. heres some pics hopefully my baby can be saved.
Phosphorus aids in root growth and overall health of the plant and is especially essential when the plant is in flowering. Cannabis loves phosphorus and it is very unlikely that cannabis gets too much phosphorus. A plant which is deficient in phosphorus will have slow, stunted growth. If there is a major deficiency, the leaves may exhibit dark gray or purplish splotches. The last picture below is an info-graphic with more information about phosphorus and your marijuana plant.
Solution: Check the pH and flush system. An excess of Fe and Zn may cause a phosphorus deficiency. If you've tried everything else, then you may try adding a bit more phosphorus to your feeding schedule and see if that helps clear up the problem. Cannabis plants love phosphorus, and therefore it is unlikely that you will give your cannabis too much phosphorus.