Hi. The structure of the seedshells changed.Some strains are very well known to have hard shell like Jack Herer, those plants like to chop of their own head with thse strong shells. But if they are out of shell they normally behave like other seeds. I( dont know how you germinate the Seeds , but here are some Tips to handle hard seedshells. a) put some seeds in a small plasticbox and shake them very well for around a minute. So litle cracks appear in the shell and it opens easier b) let them soak into lukewarm water up to 24 hours......... after that procedures a shell opens much better