Sometimes the shells are too hard for the plant to open by itself. After 10-14 days I usually crack the seeds open by hand (being very careful) and then take the little sprout out and plant it rockwool. I have "saved" quite a few seeds like this, most recently I had 6 Chronic seeds of which only 1 sprouted without help, 2 I left longer to see if they would come up but they never did, 3 I opened by hand and they are all growing strong.