Do Inderstress my plants?

You aren't taking advantage of that 1000ppm of CO2 at 26 DLI... assuming it is measured accurately. With ambient co2, you're probably fine around 35DLI. So you should be able to go higher. I'd start around that point and slowly edge upward. Realize that giving a little too much each day might takes weeks to show a visible symptom. Keep track of it - notes help. You may need to look back multiple weeks to recognize cause of any symptoms. Over time through trial and error you'll find the most DLI you can give without damage... Temps, RH% and CO2 all being important factors. 1200-1300ppm of CO2 is what you want to shoot for if you want to 'maximize' things. Might need 55 DLI or more for that much co2. Trial and error... too many moving parts to take anything too literally. Your environment will be different than others more times than not. and yea, if oyu do co2, best if the room or tent is well-sealed. exhaust should turn on to combat RH but otherwise it'd be wasting your co2 blowing it out 'the window' figuratively speaking.