Hey elmer bud I saw that this question is 6 days old and was wondering if you ever transplanted them? You are correct that rockwool is VERY sensitive to overwatering. With those size cubes you want to plant them as soon as the roots start coming put of the bottom. But once you transplant them quite the opposite will happen. The grow medium you plant them in will pull water out of the rockwool so you will not have the overwatering issue anymore. I use perlite mostly but have used the clay pebbles, soil, coco and you want to plant them in something asap. Hopefully you already have. Curious to see an update on how they are doing. Good luck!