My plants look like they had enough of this world

Morning Folks!
I am on my first grow and sadly I opted for a RDWC already made system. The plant!t aeros 4. I am getting overhelmed.
So I have 4 AutoNL from 00seeds aquired through seedsman. They are 1 month old today.
I am feeding Canna Aqua at 1/3rd strength plus Rhizotonic and Cannazym also at 1/3 from what is recommended. They were under a 250 mh light until 3 days ago when I switched to a 600w hps. My temperature in the tank (60 l) went up from 20.5 c to highs of 25.2 c before the lights go off. I keep them on a 18/6 schedule.
i have been reading and reading and reading on different websites and so on.The most popular seems to be a water chiller device. Problem is it’s pretty hard to get one where I live, not to mention the costs and the limited space I have.
I am currently waiting on a Z7 water conditioner that seems to have been working for a small faction of people that are not that sold on water chillers. Z7 claims that will provide a bacteria, rot and fungus FREE environment for them roots.
PH has been a bitch to deal with it since the canna is using buffers so it should be oscillating around 5.8 but stayin in the range that plants love in hydro. Or at least this is what they claim.
Hope this paints at least a sketch if not a picture of my setup.
Now the issue is that the lower leafs had started discoloration.
I just checked on the roots now and it looks like rot starts settling in. I ll add pictures but they are pretty yellow from the hps

I am going to do a res change for now and probably scale the hps down to 400w since the ballast I am using it’s a dimmable Lumatek.
Any thoughts would be greatly apreciated.
I now I haven’t been much of a contributor to this comunity but I really don’t have much to contribute at this point in my ganja Journey.
Thank you all for your time and advice

Morning again !
They look better already. I have changed the reservoir and mixed in nutes at 1/2 strength. I also lowered the hps to 400w. I know it will chip away at the quality and quantity output since it’s a 600w lamp but I am willing to buy a new one in 6 months.
Temperature in the tank went as high as 23.1 wich is progress in my book.
I am looking forward to receiving the miraculous Z7
Anyway. Some of the lower leaves have this dark shiny spots on them. I plucked’em since they looked half kaput.
Would be nice to hear any kind of feedback. When you all wake up that is.

on the first picture i have had this, not severely though, and i usually change the resovior and it resolves, although i dont know the cause, so could anyone give any answeres? im kinda new myself to this, and im using a dwc styled setup

Tinsler said:

on the first picture i have had this, not severely though, and i usually change the resovior and it resolves, although i dont know the cause, so could anyone give any answeres? im kinda new myself to this, and im using a dwc styled setup

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Thanks man!
The reservoir change seems to have worked. They look nice and hungry. Good luck with your ladies!

i also noticed over the last two days, i pulled back the amout of water flow to like half and they seem to like it, so overwatering you could watch out for, and thank you, i hope they do really well! as with yours! Good luck man