You don't say what kind of lighting you are using, but without more information I would guess, not enough light and possibly too warm after germination. Lower room temperature, more light usually helps to produce stockier sturdier seedlings. You want to encourage good root development while still indoors, top growth and height are secondary.

I agree 100% with morz8 and would only add a fan to provide air movement. Al

I would also chime in with don't add any Nitrogen-based nuits. Seedlings don't need it.

Mike