Try perlite, alot of people have problems with rockwool. It holds too much moisture and has ph. So you have to soak them overnight. I tried coc peat in soil, 50/50 perlite and coco and it was way too wet. The plant didn't dry out for 3 days, so I repotted in soil and the plant started to grow. Coco is so small it will clog your pump in no time if you are recirculating. I've heard alot of good things about perlite. I want to try that next. Perlite floats, so does hydroton.

Are you talking about Oasis cubes? The stuff florists use to make flower arrangements? Your plants look good man. Keep up the good work. Make sure you have a ph meter and ppm meter. You will need to adjust the ph of the nutrient solution and check nutrient strength.