There is about half a gram of nutrient salt in a liter of ec0.7 spray. A couple of grams of gloopy wetting agent, and usually some amount of seaweed stodge when I spray.
When that drys off, it leaves marks. I'm not sure why you havn't seen this. If you run tap water over a clean glass and allow it to dry it leaves spots. With nothing added at all.
So plants DO NOT transpire at night? Or just transpire less at night?
After lights off plants continue transpiring, even when not running co2. Its good to have an exhaust fan/dehumidifier to mitigate the issue. Stomata are mostly closed at night so co2 isnt really needed in abundance.
CO2 is indeed functionless at lights out, but I think the drop in temperature of lights off is what generally causes RH to spike, rather than the plants spitting it out.
https://www.lenntech.com/calculators/humidity/relative-humidity.htm
28*C at 50% RH is 12.04g of water / kg of air.
lights go out, and temp drops to 20.
20*C at 82% RH is 11.99g of water/kg of air.
Makes sense, it was something DunHav`nFun said that stuck with me over the years. Could be a combination of both since indoors plants are at their max rate of transpiration when the lights turn off abruptly.