Hindu Kush Auto GC Seeds

Flowering looking good still seeing the rusty brown spotting on upper fan leaves and drying out. I included pic of what it looks like. Since I was only using tap water and tiger bloom 3-4 tsp per gallon I gave it a rest and then just used cal-mag 1 tsp per gallon through the next few waterings. Not sure why this sometimes happens. Most things I read point to either deficiency in calcium or magnesium, but I believe the tiger bloom have some of that in there already. I know the tap water has calcium. Maybe it was too much TB? I was being pretty aggressive with it at 4 tsp per gallon. Other than that I am not stressing over it. I have lowered dose of TB to 1 tsp per gallon every other watering. Temps are low 60s and humidity is in the low 40% now. Only using the flower switch on my light considering the distance from my lights is about 10". Buds are developing nice though it seems.