Still no pictures, 4 pages in, but often rust spots are a magnesium def...
Disclaimer: I still use HID and I'm NOT an LED expert. All of my LED knowledge is from other parties or research so I can't say from first hand experience one way or another. I also run a medical grow consulting business in SoCal.
plants were doing just fine and then I for got the UVB light was on . when this happened their was just a few spots, and now im starting my 6th week in flower . so after I left the UVB light on for 4 hr ,less than 24 hrs later the spots are all over the plants .