There could be several reasons why they are not rooting well. 6.3 may be acceptable, but I wouldn't bet on it. Also, I hate rockwool. It's very difficult to keep the moisture level just right. RW likes to hold tons of water. Mine were always too dry or too wet, mostly too wet. You don't want your RW to be wet, you want it moist. Too wet and they will just rot. If you've got no roots after 2 weeks I wouldn't count on getting any. A rooting hormone would help but they should root without it as well. I like powders or liquids, since gels seem to seal off the cutting from all moisture uptake through the stem. Do you scarify? It helps a great deal. And no need to apologize about your avatar. Very different, scary, interesting.