Should of been told a week ago to seal them rockwool holes around the stems, should of been done straight away and they should be rooting pretty much by now or just starting, also that rockwool should be not wet but just damp, by flciking them with your wrist over the sink till pretty much no more water shakes out, put in dome completely shut for two days!, Then open duct holes half way for 2 days...then completely open two days after than, should start the roots forming, my strike rate is 90%+ doing it like that, some just never root.
As suds mentioned , air embolism in the stem..you MUST cut on a 45/90° angle across the bottom of the stem then dip it straight into water or cloning gel asap to seal the cut.
Anyway keep practicing , i failed my first batch by not knowing the few things i mentioned