it sounds like you got clones with no roots givin to you. if they didnt have roots showing they should have been in a humidity dome until they did. since you have been using clean phd water i would venture to say the damage your seeing is mostly caused by moisture stress, especially the wilted one.
this is 100% dead on.
great advice butt!
butt has been doing his homework. if all 8 of them had roots when you put them into the 5" cubes , then you are way over watering. they should have spit out roots a few days after being put into the bigger ciggerette butt...i mean rockwool cube.
first off , you hurt them by using food for a ph up or down. those dont need much food at all. 1 or 2mls per gallon is plenty for those to feed.
now "flushing" is just what it sounds like. it does not matter how you do it. the object is to "clean" out the medium with water. so in your case there are many ways to do that. just dipping them in an out of plain water will work. (just keep doing it until
you feel they are rinsed out good)
running water
through them is the most common way. (just place the cube in something with holes in the bottom, an run lots of water through it. it dont matter how much water you use , as long as its enough to rinse it real good. a half gallon or 20 gallons is fine..... (a liter is proly not enough) )
as far as heat goes.... the babies dont need much light at all , so you can put that light at the very top of the tent if it will help. (or even use floros for now)
so all in all i believe you are keeping them way too wet an they are starving for o2. (number 1 factor to good growing is aeration .... to me. number 2 factor is nutrition.)
let them dry out a lot more before giving them more water and them roots will pop right out.
whatever system you put them in , control the moisture yourself for a week or two, till the roots start growin again.
your doin great ! you can ONLY learn from mistakes , an books.... never from perfection.
soil