Yeah man, those got fried, %100.
I dont personally thinkkthey'll come back for the most part, and even if they do, you might of already stressed them to the point of genetic degredation.
The ones that are taking, let them keep goin, , I would personally immediately take out the ones that are all drooped aas they will probably start to rot in a day or so, and that can spread to any that did take.
Totally correct on the fact that the cut needs to have contact with the medium, rockwool in your case.
I use rockwool for years, no heat mats, just hygrozyme 2ml/gal, and have them in domes at around 75-80F, enough water/solution in the bottom so your rockwool can wick up any water is needs, changing it out ever 3-4 days. Should have rooted cuts in 2 weeks,\.
I recently switched back to organic plugs which I absolutely love and prefer. They root faster, have a better texture, better air:water ratio, and are like sponges. you can cut a slit, open it, put in the clone, and it hold it perfectly on every bit of surface area. I get almost %100 results with them every time.
As long as your ambient temperatures are proper, you dont NEED heatmats. Maybe if you're having problems with a particular strain, then bring it out for extra measure, but you shouldn't need it.
I like Rootech gel personally, and hygrozyme, no nutrient needed. With some that were already rooted in the past, and started needing nutes, I've used GO Bioroot, and hygrozyme, at 2ml Hygrozyme, and 1ml Bioroot per gal, or drops if your going by a quart or something. Superthrive is decent stuff too.
Hope I could be some help.
-peace
Halfstep