First time led grow

Timer for lights have been set to 18 6 since week 2 not too sure if it's normal for a plant to take this long to grow in leds never used LEDs before overall plant health is excellent no root rot no bugs and now have it in my closet lights 18 inches away if somebody can give me some tips or explain to me why the overall plant height isn't growing but it's growing out faster than up 3 inches wide 2 inches tall stem isn't very thick yet hopefully it'll start shooting up in the next couple weeks