What kind of deficiency, (calcium)?

[Leovaldez]

Hey everyone, I’m in my 4th week of flowering and now ran into problems. Before this week everything looked great but now I have leaves getting brown spots and becoming brittle. Any help would be amazing on what this is and how to fix

Info:
650w VIVOSUN grow lights
Fox farm ocean forest
12/12 light
Only given small amounts of FF big bloom nutrients
Water every few days in 10 gallon fabric pots

 

[ArtfulCodger]

When there are light spots along the veins in flower, my first guess is potassium.