In pro mix.....my pH is always perfect at 6.4-6.5. Not over fertilization as I've been running at 1000 ppm. It's only at the top of a few plants, which tells me it's probably a "burn" of some sort. Again, I'm flushing tonight and will cease using the silica for a week or two. I pinched off the worse of the leaves (just a few). The earlier guess of a virus would have been my guess too but I'm 80% sure it's over fertilization of the silica. My other room plants are perfect with no signs of any issues. This room always gets a higher dose of ferts, which leads me back to the silica. The SNS 209 is all natural and the Snowstorm I applied once at a minute dose so I'm sure that's not it. Thanks everyone......