Yellow rusting leaves

Indoor grow
Banana Kush
2 plants in 5 gal fabric pots with reflecteex(sp) wrapped around pots fr insulation from recent cold
Roots organic lush soil
Early flower 57 days from germ
Sonofarm light P100 16 inches above canopyI ml cal mag 1/2 ml fish shit every watering… 39 days from germ I started flora trio .7 ml micro .7 ml .7 ml bloom. Have worked up to 1ml micro 1 ml grow 1.5 ml bloom
At day 57 feeding every other watering 2L water every three days. Have not PH’d the water (soil grow)
68-78 temp range RH 35-50%
7x15 grow room with split unit for heat and air
2x2x5 grow tent
No pest as best I can ascertain

The pics show my concerns. It seems to only affect the older growth so far. Any help appreciated.