Less true in hydroponics. Problems usually show themselves in 12-24hrs. That said, damage never really heals. Those leaves may have gotten too hot (closer to the light) and crisped a bit. Keep an eye on them but mostly watch the newer growth. It’ll tell you if something is still amiss.
You have a shorter window before issues appear, and a shorter window to wait before they’re fixed once you make corrections. “Major damage” is kind of extreme. I have only killed 2 plants in hydro thus far and I’ve ran upwards of 20ish by now. One was beginner problems, one was overconfident problems.
What light, specifically, and at what power?
Just to give you a heads up here, 71° is going to be warm. It’s a hit-and-miss thing, that might be absolutely no big deal, but if any light at all is getting into your reservoir, you’ll be facing root rot and other problems before too long. Ideally in hydro your water should live between 66-68°F. Don’t stress it too much, but do double check your hydroton is sufficient to keep any light out.
And you’re only 36” from the top? I might raise that up another 4-6” and see how she responds. A 650R is a boatload of power. Mine is pretty creepin’ hot after it’s been on for a few hours. I bet her leaf temps are just getting a little toasty.
Roots are not out of the bottom of the net pot yet, ppm is at 680, as for the water level, I have it right at the bottom inch of the net pot which is about where the bottom of the roots were. The reason that the roots aren’t out of the bottom is because the net pots I bought were the ones that fit into the bucket at the store which seemed a bit big, but I didn’t figure it would do too much harm.
Lower your water level about an inch below the bottom of the pot. She’ll start reaching roots down to reach the water and the airstones in the bucket will bubble water up and splash the hydroton so she shouldn’t totally dry up.