I was looking at the white spots on your leaves. Have you put them under a microscope or loupe? Anything on your leaves that looks like dust should be inspected. White flies, aphids, and mites can look just like a spec of dust !
The black spots are not good and as someone said it could be a fungal problem. The brown spots could be a lot of things (its happened to me often). Have you inspected for pests? Any chance you have some ants crawling around? If you dont get this figured out soon, all hell will break loose, the timing isnt good !
It's funny, they tell you to follow the feedcharts, (fox farm as an example) and when you do, they call you an idiot. If you have salt buildup and lockout after the stretch, your plants are starving anyway. A flush can only help in this situation. (or if your PH is off)
If its fox farm soil your in, check the soil PH asap.... Mine has dropped to 5.0 and less midflower and a flush cured it.
last tip, cut the bloom nutrients recommended by fox farm to 1/4-1/2 what they recommend... DONT USE THE BLOOM BOOSTERS cha ching, beastie bloomz etc...