Stem borers can cause what looks like a mysterious deficiency before fucking up your whole plant. I was dealing with it alot on my flowering plants in early summer thinking my nutes were bad before I finally found some tiny 1mm bore holes in my stems, some of the holes actually heal over and you have to scrap the stem a bit to expose it and the fuckers are still alive inside your plant.
Just a tip, if you have been on point with your feeding but can seem to beat a deficiency. There are several different stem boring insects that affect cannabis.
