The fogger might be drowning the roots if it is continuously ran... you need lots of Oxygen in the root zone! ...id maybe stop the fogger and feed the plants from the top of the net pot until the roots are long enough. What method of hydroponics are you growing with? do you use air stones to pump oxygen into your nute solution? you cant just have your roots sitting in stagnant water, even in Ebb-n-flow (Flood-n-drain) you want to put a few air stones in your res to keep the nutrient solution well mixed and aerated.

Your PPM's were high, good choice on switching over to RO water, maybe that will help.

To me it does not look like a deficiency, it looks like nute burn! make sure your pH pen is calibrated correctly with pH calibration solution (I no when i purchased BOTH my pH pens from the hydro-store they were NOT calibrated correctly and i had to purchase calibration solution)

Make sure you are checking your pH OFTEN! ....you can not check it enough in 1 day.... i check mine almost every time i walk by the grow room (some times up to 7 or 8 times a day!)

...im rly surprised your not having pH swings considering u didnt rly rinse or pH your stones. usually if u dont rinse//soak///rinse//soak (keep doing it) until the water you rinse is the same pH as when u soaked

I hope i read that wrong and your pH in your nutrient solution is NOT 8.5...