Weird Germination Problem

5 seeds originally placed in rockwool/aeroponic cloner system. 3 of the 5 had starter leaves in 2-3 days. The other 2 however have yet to sprout.
I decided to open the rockwool and found that both seeds had cracked. I could even see the white root, but it was still stuck in the shell.

What's going on? Are they garbage?

where were your seeds from? that always seems seems to happen to my "freebie" seeds included with various orders.

Single Seed Centre