Brown spots on older leaves

I have some lavender kush clones in coco 24hr veg. I'm feeding them 1ml roots excellerator 4ml silica blast 5ml calmag+ 8ml liquid karma 10ml pure blend pro. Alot of the older fan leaves r getting brown spots all over and are startin to get a lil yellow. Can u tell me wats wrong n how to fix? Thanx

pics help? People will want to know the pH.

Ph is about 6.5 transplanted 2 weeks ago

I have a 400w mh n a 400w hps light tuning 24 hrs temps 73-80 also found wat I think is an aphid so I hit them all with bayer advance frit citrus & vegetable insect controle

To me looks like cal def caused by wrong ph, if u grow in coco use PH 5.8

You have calcium and magnesium def and that's a fungus gnat

How do I get rid of the fungus gnats? Will the bayer f,c,v insect controle help?