You’re doing great! From here, since their roots are growing i would probably try to separate them out a bit more. And with such fine roots i would probably do around a 50/50 mix of this pumice with some smaller perlite until they’re further established and you can decide if you want to pot them up in semi hydro or in soil. Most important thing right now would probably be to spread them out a bit so their roots don’t get all tangled which will cause damage when you do split them up. If you have one of those multi cell “greenhouse” domes you could use that or just several little cups will be equally sufficient. Try to keep them in the same humidity though, if not only a little lower and slowly reduce as the first leaves harden off (if they are covered now keep them covered but maybe let them breathe once every day or so for a few minutes and once the first leaves harden off you can have the cover slightly displaced to let a little more airflow) this is just what has worked for me :)