Hoys seeds from the same pods grow at different speeds

Hoya cv Joy and Hoya elliptica seeds : these 5 Hoya elliptica seeds in picture below are from the same pod, they were packed the same day in the same conditions : amazingly 2 of the seed lots are growing much slower than the 3 other lots. Why is it the whole lot and not just a few seeds in the lot ?? Would seeds have a communication of some sort ??

The same questions arises with Hoya cv Joy : all the seeds in 1 of the   packs are grwing much faster than all the seeds in the 3 other packs.
 Seeds are available from www.aleyagarden.com
http://www.aleyagarden.com/hoya_seeds Exotic plants are available on http://www.aleyagarden.com/orders__transport_costs