I have a similar looking problem on a couple of plants and have been trying to decide if it is rust (fungus), which I saw all over a tree in my yard, or a phosphorus deficiency. For me, it seems to only affect plants in mid or late flowering. As I am a recovering over-waterer, it could be that (although RH stays steady at 45-50%). I'm using FF Happy Frog, which seems to drain pretty well. Since flowering, I didn't want to spray and dipped some leaves in a garlic dip and sprayed H2O2 (hydrogen peroxide) on the soil surface, pots and surrounding grow area (tables, trays, etc.). Temps under HPS ranges 74-82 F. I took some pics, but don't know if you can tell anything from them. I'll have to get my girl to take some pics with the good cam later. Goat's pics look like what I'm seeing. Any thoughts?

Also, recently had some cuttings that had brown spots on leaves, a new thing for me. 2 other new factors that round, filtered tap water instead of distilled grocery store water and cloning in soil instead of peat pellets. The spots disappeared or discontinued on the cuttings I kept.
feefigreenthumb Reviewed by feefigreenthumb on . Brown spots on leaf tips of clone- So my buddy took a clone from me. It has rooted fine and began to grow. I learned afterward that the soil he cloned the plant into was the miracle gro fertilizer in the soil type. The plant was transplanted into a larger pot with good soil (but the initial root mass is still in the fertilized soil). Plant began to grow fine for a few weeks, then all the new leaves (and old too) began to get small brown spots on the tips. Then the spots began to move closer to the stem. Now, it has Rating: 5