Spider Farmer Spooky Bonsai Bonanza

1 month into flower, canopy nice and flat with healthy buds fattening nicely. Thrips seem to be totally gone but I'm leaving the yellow traps there just in case and monitoring carefully. (Nursery in the same room with the sf1000 has fungus gnats that we are working to knock down). No smell yet from the GDP and haven't bothered to filter exhaust air as a result. New 6" exhaust fan plus the 16" Hurricane keep temps right around 25C with the @spiderfarmer se7000 at 80% power, and 18C with the light off at night. Grow is in my furnace room so it's quite dry, especially during the winter. Last week I started noticing brown spots on some fan leaves that look like a calcium or magnesium deficiency. This is strange, because I have been feeding 2ml/L CalMag, but I have been adjusting nutrient solution to 5.9-6.3 so I am beginning to suspect nutrient lock out due to low PH. I will water at 6.5-6.8 for a week and see if I can get the brown spots under control. Yesterday's watering was at 6.7 and runoff was 6.3, which lends evidence to my theory that ph might have been too low at the roots. (Note: I'm starting to think that my VPN might have something to do with my photo posting problems from earlier weeks. Posting today from work without issues.)