Personally, I think this is recoverable. The plants are big, so the stuff at the bottom is not useful anymore. Cut all that lower airy stuff, and yellow leaves off and the plant will get better air circulation, and maybe supercrop the main stem, but I'd wait till they pick up a bit.
As
@Mañ'O'Green said, water the plants well, wait an hour, work out which direction you want the stem to go, then give the main stem a good squeeze until you feel it pop inside. Do that up and down for an inch or two, then bend the stem to 90°, and support it. You will be fine and you wont regret it.
Regarding heat stress, I have to deal with this a lot. I switched from HPS to LED and that helped. With the HPS the heat stress caused a lock out, the plants stopped drinking and they wilted like yours.
So if that's happening to you, lower the EC by a couple of points and add some Kelp, the added micronutrients will give the plant a boost. The leaves won't straighten out, but the new growth should look OK as they recover. I used a fan to push the hot air directly under the lights up towards the carbon filter, and a nice big floor fan to push cooler intake air upwards into the plants.
Hope all goes well. They are amazing plants, and put up with all sorts of shit, usually bouncing back better than ever. Those large yellow lower leaves were depleted by the plant to help it grow. They have done their job so get rid. Same for the airy bud, strip it all off.....
let the plant concentrate on what's up top!
Day 30 is not too bad, they are just about to flower, so they need a bit of TLC and away they'll go!