You have a lot of light in that space.
Try to remove the kinks in the fans cooling your lights. 90 degree bends restrict the air flow.
Is that a portable ac unit? If it is, then it will exchange air unlike a mini split system so it is removing co2 from your room when its on.
Your in between...
DWC is one of the least complex growing methods. It can be a bitch though if your temps are high and oxygenation isn't enough for the roots.
Good luck!
All you need is air. Leave the air pump on for 24 hours. If you want, you can make it a recirculating dwc system by using the air pump and a drip emitter but is not necessary.
In dwc, you always need oxygenation. If you would turn the pump off even at night you can get root rot.
As long as the room stays at the right temp then you can shut the intake and exhaust fans off at night. I would keep the one in the room on though. This will reduce your chance of mold. As long as your fan isn't causing the leaves to dry out and burn then its okay.
By fan you mean a wall fan or one that is meant to circulate air within the room right? If it oscillates or is blowing lightly across the tops then leave it on for 24 hours. I have always left mine on all day and night and have no wind burn or mold.
What does your local water report say about your water? Is it less then 250 ppms? Fluoride is in all water in the U.S. and doesn't hinder the plants. If your water is soft then there is no need to filter and boil it.
Haven't got a chance to read through your thread yet but noticed right away your ballast is on the carpet. Word to the wise, move it off the ground to avoid accidental water spills and flooding, and heat + static electricity from the carpet. Plants look green though!!
J
3 Fresca Sol platinums (vertical)
3 1K Sunmaster HPS
3 C.A.P. Nextgen Ballasts @ 240v hung from ceiling
Co2 (bottle for now, burner later)
96 gallon Res for fresca sols
1/4 hp eco plus chiller for lights
mag pumps for water system
C.A.P. Ebb and grow Hydro system w/ 2 expansions (24 pots...
Your growing in an ebb and grow.
If your room gets to 90 degrees then your reservoir is getting close to that as well. Your also using an organic mix fert which doesn't bode well at those temps in this system. Im surprised your not bacteria ridden and starting to get root rot.
You should...
That meter is the same pen as the one Milwaukee makes but most likely generic. My bet is it works great considering my buddy has used it for the last year.