You have a secondary infection of Septoria. This comes about after the weakening that occured with the fungus nats. The nats actually lay eggs at the stock of your plants. These eggs are found under a microscope in the upper portion of the root mass. They can cause root rot fungus to come about in wet soil or hydro systems that can be carried to all your plants in a hydro system in a matter of days when it occurs. The black spots are typical with the yellowing, brown, and dying fan leaves. They typically start at the lower portion of the plant and move up, but I have seen it occur in the middle section and then take over the lower and upper areas. You got it, from what it sounds like, and it can devostated your crop. It is controlled by copper sulfate, neem oil in spray and added to the soil/hydro..., diatomaceous earth added to soils, white sand layers on top of soil to help prevent nats from reinfesting and laying their eggs, taking your plants out of their net pots, in in aeroponic system and removing eggs under highpowered inspections (not a good way to save the plant, but helps to reduce eggs in crop, takes forever to do, trust me on that one), cinammon powered extract and clove extract oil, sulfur burner, and raising the pH of nutrients. You need to treat with strong solution of hydrogen peroxyde if you are in flowering and sulfer burner if in early mid veg. Sulfur will leave a taste in crop. UVC light in both your crop and your hydro solutions are supper important to helping to control out breaks in later crops. You should consider stopping this before it enters your roots as it infects the plant from inside, kills the leaves from within, then spores form on the surface of the leaves (those black spots you see), and treat surface spores in your grow area by germicidal florescent bulbs in grow area. These bulbs do cause skin cancer without leaving even a burn, but do not get exposed. They rearrange DNA, which kills bugs/germs/fungus..., people/plants too... Treating plants is done in ten minute intervals with 30 mins for three treatments of ten minutes per day, no more or it will hurt plants. So, get the UV water treatment system at your local pet store for your hydro, and get a GE G36T8 bulb at your local industrial lighting supply store for about $70.00 each. The bulbs are 36 watts and are 48" long and fit in a standard T8 48" fixture you can buy at a big box store for under $30.00. It will pay off with big rewards as you have already lost that amount in electrical bills, seeds, nutrients, time, efforts, and most of all buds. If you are a professional farmer and you know how to identify this early in the veg you will loose roughly 30% of the crop. It hits novice growers hard, real hard, in all cuttings will continue to plague you. Now that you have these pests, welcome to the club, this is no joke, your crop, and all future crops are at stake, spend the money on UV setup and don't expose your self when it's on. You treat with UV when your other lights are on. UV will increase THC production by the plants and you will have the spin off of some of the best stuff around. Now that makes buying UV lights worth doing. Something to say about the trade off on the hydro UV treatment is that you will kill all benefical bacteria in the system if you add benefical bacteria to your nuts'. Guess what, you can live with not being all natural, but your crop might not be able if you have the spores all over your house and waiting to reinfect your next crop no matter how much you clean in between. It's not nutrient burn, or lock up, you have all the tell tale signs of Septoria. For now, break out the hydrogen peroxyde and drench your plants with the spray of it, add it to your nutrients, and even flush with it, and you might recupe something worth your time and money from this crop. Next crop I would advise switching to a very hearty indica that is mold resistant and treat your nutrients with H202 (15-30 mls/gal), UV treat your hydro nuts too, and treat the crop and grow area every day with UV germacidal too. You may also look at making sure your air turn over is correct, you can add a sticky filter air intake filter to help reduce incoming spores to your grow area in general. This is a filter that you add to your air conditioning system and/or central heating system. They replace your home paper filters with a sticky type. They can trap spores in the home area to reduce exposure levels in surronding areas. You can treat carpets, floors, and walls with H2o2 and UV light by the way... Welcome to mold controls for the infected grower 101. It stinks, but you got, that much I am very sure of... Good luck, and you might want to invest in Save your Garden by JC Stitch. It is on amazon for kindle for about $10 and there are photos of the fungus under the section on fungus infections for mmj.
