Thanx for passing in Evilscotsman ! unlucky on your first attempt mate ! hope i can help ye some !.......
What i do with the rockwool cubes is put them in a bucket of tap water for 3-4 hours till they get to a softer sea sponge like texture , then when theyve softened i then ph the bucket of water to 6.0 and then take the cubes out . ! Then once got the seedling in the rockwool cube i pour nutes out the res over the seedling cube i think once every few days to keep them damp !
when using low 300ish ppms i can use the nutes straight out the res pouring on the rockwool seedlings without worries of burning .
think its usually around 2 weeks time till the roots have came out enough through the bottom of cubes to be ready for the nft tray !
cheers dude , hope its gave ye some forward motion !