Lighting question

hey guys (my first post oooooo exciting)
I've recently started my first grow but am having some difficultys.
Firstly despite having sprouted over a week ago my plants still haven't grown their second true leaves and seem to be growing up too much (they're already 4 cm high), i currently have them under 12 hours of natural sunlight then 12 hours under a 20 watt lamp. I have a 150 watt hps, but it seems like a waste of electricity to have this going when the leaves are so small.
Whats your verdict on this? should i use the 150 watt lamp now or wait?
Thanks

If they are getting really tall then the light is too far away and they are stretching out to try to reach it. So either get the light closer or brighter. Good luck on your grow and congrats on your first post.

ur first problem is the light is only 20 watts u need more than that the light is also too far away with a 6500k bulb u should be about 3 inches away.