High Dabbledo
When reading the first post on your setup etc I notice that you are running pretty much all your nutes at the max listed on the labels. I use Sensi/Connie/Rhino/BigBud and some other calmag for my DWC, I rarely change all the nutes but monitor the PPM and add small amounts of nutes to keep the PPM at the level I want. I also use only RO water that I test before using as one of the stores I was getting it from rarely changed their filters and were selling RO that was over 200ppm. Barely better than town water that runs around 300.
The damage I see on your leaves is so sporadic it can't be something like a deficiency/lockout or whole classes of leaves would be showing the same thing, Some of it almost looks like insect damage and some looks like water damage. Do you mist your plants at all? Droplets of water will cause problems either burning under the lights or fungal/mold infections localized to places the water stays.
You say you have low PPM city water. How do you know and have you got a water quality report from your city to see what else might be in your water? Even if it's reasonably low in PPM that reading may be something that messes with your plant. I doesn't take much extra stuff like iron, manganese, sodium or even chloramine if that's what your city uses to kill pathogens like many do. Even if they use chlorine that you can evaporate out of the water it creates chloramine when it reacts with bacteria and organic matter in the water and does not evaporate out of the water. It's the chloramine and not the chlorine that makes your eyes all red if you swim in a public pool.
Your plant looks real good overall but if you haven't got one yet you should get a PPM pen and some calibration sol'n to test it with. My 15 year old Hanna still works fine and I recently got a new one for $25 that will read single digits until it gets over 200ppm then it switches to 10x for higher readings. The last 4 jug batch of RO we got Friday reads 12ppm which is really decent. I diluted some of my 1000ppm calibration sol'n down to 20ppm using drug store distilled water that is 0ppm to make sure it can read properly at such low levels. It read 19 so I know it's near dead on. The new pen is only used to test the water and the Hanna gets used to test my nute strength. As I use the pH Perfect nutes I let my pH pen dry out for storage and haven't used it in close to a year.
I would recommend that you use RO water for the rest of the grow to rule out water as being your problem and get a PPM pen if you haven't already.
L8r