HELP! DWC auto grow rusty spots, necrosis, root rot

[o0644]

Running RO filtered water testing about 20-30ppm, replacing water weekly. Changed water yesterday. 1 gallon, adding 3 drops of sitech, <1ml calimagic, 0.5ml general hydro floramicro, 1.5ml florabloom, 1.5mL 3% hydrogen peroxide. Was running azos, great white and southern ag b747 garden friendly fungicide but it wasn't working out, trying sterile tek now.

Seemed to be getting nitrogen toxicity so stopped using floragro. Last mix tested about 500ppm. Earlier mixes were over 1000ppm especially as the water level went down in the reservoir. I keep having to add pH down the next day after watering (was 5.5 last night, 6.4 today). Was hoping leaves wouldn't keep dying after reducing nutrient strength, but they look worse than yesterday. The water looks clearer than it did last night but the ppm didn't change that much. Maybe it went down from 600 to 550?

Is it possible I was mixing too much other stuff and not enough calimagic? Maybe adding calimagic after adding nutrient solution is no good?

The shirt is an attempt to keep light from the reservoir. Ideally I would have painted it black, then white over it to reflect light/keep temps down.

Water pump died a few days ago so I got an aquarium air pump.

4' ACI tent kit with the 100ish watt LED. Temp 74-79F humidity 55-62%
Air filter keeps getting clogged with diatomaceous earth dust.
Plant is a mephisto creme de la chem auto.

[Wayzee]

Unfortunately I can see a few problems. Firstly, do you have a feed chart for flora nutes? Should have recommended ppm and what week to use what. Next, if you're running a fungicide you don't need peroxide, most ppl here never use and dispise peroxide. Next any light getting into to resivour will cause problems. 5.5 pH is a little low for flowering, think from memory 5.8-6.4 is ok for flowering. Humidity is high for flowering try keeping temp around 75 and humidity 40-50.
I've been your position before with DWC and it sucks. I gave up on DWC and went to soil.

[o0644]

Thanks. Well it's nice not to have to refill the humidifier every day anymore. But then my temps in the tent go up more, but maybe that's fine if I run peroxide and/or calcium hypochlorite. I did a search and couldn't find much about people running peroxide on DWC here, mostly people using it to germinate seeds faster? I imagine if I keep adding peroxide before the concentration in the res goes down enough, it would be bad. Did find a thread about people trying to make a Clear-Rez alternative with calcium hypochlorite, I just ordered some pool shock that also has a few other calcium, chlorine chemicals. Will see if it kills the plant :|
I was following the charts in the bottles, but trying to go under since it's an autoflower and stressed. Maybe I'll use half strength. How much ppm would be too much?
I had similar problems with soil, maybe due to overwatering and heat.
I have the IB100 led about 18" over the plant on setting 6

[Wayzee]

The problem with peroxide is in large doses or continued use is it kills off the beneficial bacteria that the roots need. Pool shock will almost certainly kill the plant, chlorine and plants don't mix. I don't know much about auto flowers yet but going on the size of yours id say it would handle full strength especially the microbes to build a better root zone. Water temp is another killer in DWC, if your tent or room is running on the warm side your water will be to unless you are cooling it somehow. I get what you mean trying to match humidity with the temp but it's just asking for bud rot. Increased air flow will help with heat stress or a second hand portable AC cooler if you got the coin. I also recommend getting a par meter or finding a decent one you can download onto your phone ( not sure on their accuracy though) to measure how much light you have at the canopy of the plants. Another thing that happens is" lock out" if your plant has been in the wrong conditions mostly with pH fluctuation it will go into lock out and won't be consuming any nutrients. That's bout as far as my knowledge goes with this part of it. Bluey or Allenpro among others might be able to help you out further and correct anything Ive said wrong.