lol. wtf are you talking about stretching? they are growing dude. stretch refers to the space between the nodes. you have 2 nodes really, the cotlyedons and the first set of leaves, from what i can tell the space between the 2 is about 1/2 an inch?
i wouldnt worry unless the inter-node spacing is more than 2 inches or so.
leave them where they are, and in 2 weeks, stick them in 6in pots. dont bury them up to the cotlyedons, thats not always a good idea. you want some space between the dirt and the first set of leaves for airflow.
they look fine. stop worrying