If you dont have a ppm meter, go to the shop and get a few litres of bottled water, no carbonated. Fill a tuberware container up with it, PH it down to 5.8, get a glass, fill it with the pHed water, submerge the hole rockwool cube in it, take it out, cup your hand round it, leave a space between your finger and gently flick your wrist. Then get rid of that water in the glass, fill it up with the pHed water again, and repeat that 2 or 3 times to all clones. Leave them until tomorrow, and only feed them water.