Wow... A lot of people here seem to think they know wtf they are talking about with their diagnosis. 420 God is the only one with the reasonable approach, and he offers a solution rather than just a name to the problem.
The reason most people here are struggling is because there is just so much wrong.
There is most definitely a pH issue. I question the accuracy of your measuring device if your pH is infact 7.0. Your meter may need to be calibrated or replaced with an upgrade.
The rusty brown spots 99% of the time are referred to as pH spotting and it results from an acidic media locking out elements like calcium, magnesium, and potassium. Low and behold. Those are the elements listed in this discussion. So we're not far off in the diagnosis. Yes the plant is deficient... but not as a result of an under-abundance of elements in the soil. It is actually quite the opposite.
In addition to the pH issue, there is a contributing heat issue (86 degrees is not okay). Heat causes increased rates of transpiration, which utilizes elements like potassium to mobilize energy for the procedure. This then exaggerates the potassium situation, ultimately creating a domino effect.
The use of Sphagnum Peat Moss based Happy Frog Soil indicates to me that it is likely a conglomeration of issues that all started with a pH imbalance and a heat problem. These will ultimately cause more problems and you're knee deep in the thick shit right now.
Identified the problem. Now for the solution.
Start with the easy stuff. Back the light off to 18" to 21" from the plants. This will reduce canopy temperatures and the load on the chlorophyll. Think of it like driving a little less "lead footed." If your plant is a car, then you are low on gas because you've had the pedal to the metal. It is a good idea right now to slow down to 55mph and get that efficient mileage so you can make it to the next gas station.
Reduce the heat in the room. Get an AC, leave the window open. Do whatever it is you have to do to keep your temperatures under 82 and ideally around 75.6 to 76.2 all day every day. Night time temperature swings, from 80 during the day to 60 at night, is not beneficial.
You need to flush the media to balance the pH. Using a 6.8 to 7.0 pH solution run at least 2 gallons of water through the media (after saturation) to get the system back in balance. Once the media has been flushed and the run off pH is dialed at over 6.5 but beneath 7.0; then you can rebuild your nutrient buffer. Using 1-2ml per gallon of your macro system from H&G make a nice low strength solution. If you have some cal-mag around 1ml per gallon of that would be fine to add around 20ppm of the stuff to your system, not a lot, but enough to keep the plant from leaching more elements in a "reverse osmosis" fashion back into the media in order to balance out electrically. (Plant=high pressure nutrients / Flushed media=low pressure nutrients / Pressure flows from high to low).
Once the temperature is resolved, the light backed off, the media pH and CEC balanced... Then you can take a week or so to let the plant rebound and make your follow up treatment based on the current issues with the plant. You do need to drop your ppm levels in the future. 1000ppm in soil is ridiculous. If you want to feed like that then move into coco. 500ppm to 800ppm is a good range for most strains.
Good luck dude. Work on your environment before you get this far with another grow. Better to have everything dialed in.