Is this root rot?

Hello guys, i have a big problem...
This is 12th day of vegetation. But plants had temperatures up to 31C, water temp up to 20C. So they seem to be very unhappy. Is it possible to heal them and have a normal yeld? Or should be thrown away and start growing new ones?

Adding pictures. One is dead :/

that's pretty big for only day 12 of veg. i don't grow in cubes like that but i'd think there woudl be more roots than that for a plant that size.

I would trash them and put new ones in if you got them. And yes, that looks like root.

do the roots smell bad?

I never had good luck with rockwool. Holds too much water and yes you have root rot.

Get some hydroguard or southern ag garden friendly fungicide and that might save the others. I use Tribus Original, it has the same bacteria plus a couple others. Good stuff.

Also if thats flood and drain you need to increase the interval between floods. They are drowning.

Yeah, way too wet. Instead of putting the plugs into bigger cubes put them into net pots with hydro balls. Within a week or two they will split the little remaining rockwool apart and it won't matter how wet it gets. I'm guessing an Aero run like a NFT, a NAFTTY